Mr. Chief Justice HUGHES delivered the opinion of the Court.

In a proceeding under the National Labor Relations Act of 1935 the National Labor Relations Board found that the respondent, Jones & Laughlin Steel Corporation, had violated the act by engaging in unfair labor practices affecting commerce. The proceeding was instituted by the Beaver Valley Lodge No. 200, affiliated with the Amalgamated Association of Iron, Steel and Tin Workers of America, a labor organization. The unfair labor practices charged were that the corporation was discriminating against members of the union with regard to hire and tenure of employment, and was coercing and intimidating its enployees in order to interfere with their self-organization. The discriminatory and coercive action alleged was the discharge of certain employees.

The National Labor Relations Board, sustaining the charge, ordered the corporation to cease and desist from such discrimination and coercion, to offer reinstatement to ten of the employees named, to make good their losses in pay, and to post for thirty days notices that the corporation would not discharge or discriminate against members, or those desiring to become members, of the labor union. As the corporation failed to comply, the Board petitioned the Circuit Court of Appeals to enforce the order. The court denied the petition holding that the order lay beyond the range of federal power. We granted certiorari.

The scheme of the National Labor Relations Act-which is too long to be quoted in full-may be briefly stated. The first section (29 U.S.C.A. 151) sets forth findings with respect to the injury to commerce resulting from the denial by employers of the right of employees to organize and from the refusal of employers to accept the procedure of col lective bargaining. There follows a declaration that it is the policy of the United States to eliminate these causes of obstruction to the free flow of commerce....

Contesting the ruling of the Board, the respondent argues (1) that the act is in reality a regulation of labor relations and not of interstate commerce; (2) that the act can have no application to the respondent's relations with its production employees because they are not subject to regulation by the federal government; and (3) that the provisions of the act violate section 2 of article 3 and the Fifth and Seventh Amendments of the Constitution of the United States.

The facts as to the nature and scope of the business of the Jones & Laughlin Steel Corporation have been found by the Labor Board, and, so far as they are essential to the determination of this controversy, they are not in dispute. The Labor Board has found: The corporation is organized under the laws of Pennsylvania and has its principal office at Pittsburgh. It is engaged in the business of manufacturing iron and steel in plants situated in Pittsburgh and nearby Aliquippa, Pa. It manufactures and distributes a widely diversified line of steel and pig iron, being the fourth largest producer of steel in the United States. With its subsidiaries-nineteen in number-it is a completely integrated enterprise, owning and operating ore, coal and limestone properties, lake and river transportation facilities and terminal railroads located at its manufacturing plants. It owns or controls mines in Michigan and Minnesota. It operates four ore steamships on the Great Lakes, used in the transportation of ore to its factories. It owns coal mines in Pennsylvania. It operates towboats and steam barges used in carrying coal to its factories. It owns limestone properties in various places in Pennsylvania and West Virginia. It owns the Monongahela connecting railroad which connects the plants of the Pittsburgh works and forms an interconnection with the Pennsylvania, New York Central and Baltimore & Ohio Railroad systems. Much of its product is shipped to its warehouses in Chicago, Detroit, Cincinnati and Memphis,-to the last two places by means of its own barges and transportation equipment. In Long Island City, New York, and in New Orleans it operates structural steel fabricating shops in connection with the warehousing of semifinished materials sent from its works. Through one of its wholly-owned subsidiaries it owns, leases, and operates stores, warehouses, and yards for the distribution of equipment and supplies for drilling and operating oil and gas wells and for pipe lines, refineries and pumping stations. It has sales offices in twenty cities in the United States and a wholly-owned subsidiary which is devoted exclusively to distributing its product in Canada. Approximately 75 per cent. of its product is shipped out of Pennsylvania.

Summarizing these operations, the Labor Board concluded that the works in Pittsburgh and Aliquippa 'might be likened to the heart of a self- contained, highly integrated body. They draw in the raw materials from Michigan, Minnesota, West Virginia, Pennsylvania in part through arteries and by means controlled by the respondent; they transform the materials and then pump them out to all parts of the nation through the vast mechanism which the respondent has elaborated.'

To carry on the activities of the entire steel industry, 33,000 men mine ore, 44,000 men mine coal, 4,000 men quarry limestone, 16,000 men manufacture coke, 343,000 men manufacture steel, and 83,000 men transport its product. Respondent has about 10,000 employees in its Aliquippa plant, which is located in a community of about 30,000 persons.

Respondent points to evidence that the Aliquippa plant, in which the discharged, men were employed, contains complete facilities for the production of finished and semifinished iron and steel products from raw materials; that its works consist primarily of a by-product coke plant for the production of coke; blast furnaces for the production of pig iron; open hearth furnaces and Bessemer converters for the production of steel; blooming mills for the reduction of steel ingots into smaller shapes; and a number of finishing mills such as structural mills, rod mills, wire mills, and the like....

Practically all the factual evidence in the case, except that which dealt with the nature of respondent's business, concerned its relations with the employees in the Aliquippa plant whose discharge was the subject of the complaint. These employees were active leaders in the labor union.... In this situation, the record presents no ground for setting aside the order of the Board so far as the facts pertaining to the circumstances and purpose of the discharge of the employees are concerned. Upon that point it is sufficient to say that the evidence supports the findings of the Board that respondent discharged these men 'because of their union activity and for the purpose of discouraging membership in the union.' We turn to the questions of law which respondent urges in contesting the validity and application of the act.

First. The Scope of the Act.-The act is challenged in its entirety as an attempt to regulate all industry, thus invading the reserved powers of the States over their local concerns. It is asserted that the references in the act to interstate and foreign commerce are colorable at best; that the act is not a true regulation of such commerce or of matters which directly affect it, but on the contrary has the fundamental object of placing under the compulsory supervision of the federal government all industrial labor relations within the nation.

If this conception of terms, intent and consequent inseparability were sound, the act would necessarily fall by reason of the limitation upon the federal power which inheres in the constitutional grant, as well as because of the explicit reservation of the Tenth Amendment. The authority of the federal government may not be pushed to such an extreme as to destroy the distinction, which the commerce clause itself establishes, between commerce 'among the several States' and the internal concerns of a state. That distinction between what is national and what is local in the activities of commerce is vital to the maintenance of our federal system.

We think it clear that the National Labor Relations Act may be construed so as to operate within the sphere of constitutional authority....There can be no question that the commerce contemplated by the act is interstate and foreign commerce in the constitutional sense....The grant of authority to the Board does not purport to extend to the relationship between all industrial employees and employers. Its terms do not impose collective bargaining upon all industry regardless of effects upon interstate or foreign commerce. It purports to reach only what may be deemed to burden or obstruct that commerce and, thus qualified, it must be construed as contemplating the exercise of control within constitutional bounds. It is a familiar principle that acts which directly burden or obstruct interstate or foreign commerce, or its free flow, are within the reach of the congressional power. It is the effect upon commerce, not the source of the injury, which is the criterion. Whether or not particular action does affect commerce in such a close and intimate fashion as to be subject to federal control, and hence to lie within the authority conferred upon the Board, is left by the statute to be determined as individual cases arise. We are thus to inquire whether in the instant case the constitutional boundary has been passed....

Respondent says that, whatever may be said of employees engaged in interstate commerce, the industrial relations and activities in the manufacturing department of respondent's enterprise are not subject to federal regulation. The argument rests upon the proposition that manufacturing in itself is not commerce....

The government...urges that these activities constitute a 'stream' or 'flow' of commerce, of which the Aliquippa manufacturing plant is the focal point, and that industrial strife at that point would cripple the entire movement....

The congressional authority to protect interstate commerce from burdens and obstructions is not limited to transactions which can be deemed to be an essential part of a 'flow' of interstate or foreign commerce. Burdens and obstructions may be due to injurious action springing from other sources. The fundamental principle is that the power to regulate commerce is the power to enact 'all appropriate legislation' for its 'protection or advancement'; to adopt measures 'to promote its growth and insure its safety'; 'to foster, protect, control, and restrain.'  Although activities may be intrastate in character when separately considered, if they have such a close and substantial relation to interstate commerce that their control is essential or appropriate to protect that commerce from burdens and obstructions, Congress cannot be denied the power to exercise that control. Undoubtedly the scope of this power must be considered in the light of our dual system of government and may not be extended so as to embrace effects upon interstate commerce so indirect and remote that to embrace them, in view of our complex society, would effectually obliterate the distinction between what is national and what is local and create a completely centralized government....

It is thus apparent that the fact that the employees here concerned were engaged in production is not determinative. The question remains as to the effect upon interstate commerce of the labor practice involved....Giving full weight to respondent's contention with respect to a break in the complete continuity of the 'stream of commerce' by reason of respondent's manufacturing operations, the fact remains that the stoppage of those operations by industrial strife would have a most serious effect upon interstate commerce. In view of respondent's far-flung activities, it is idle to say that the effect would be indirect or remote. It is obvious that it would be immediate and might be catastrophic. We are asked to shut our eyes to the plainest facts of our national life and to deal with the question of direct and indirect effects in an intellectual vacuum. Because there may be but indirect and remote effects upon interstate commerce in connection with a host of local enterprises throughout the country, it does not follow that other industrial activities do not have such a close and intimate relation to interstate commerce as to make the presence of industrial strife a matter of the most urgent national concern....We have often said that interstate commerce itself is a practical conception. It is equally true that interferences with that commerce must be appraised by a judgment that does not ignore actual experience....

Our conclusion is that the order of the Board was within its competency and that the act is valid as here applied. The judgment of the Circuit Court of Appeals is reversed and the cause is remanded for further proceedings in conformity with this opinion. It is so ordered.