http://www.laborrelationsupdate.com/nlrb/nlrb-all-employers-must-post-notice-informing-employees-of-rights-under-nlra/

SUPPLEMENTARY INFORMATION

I. Background on the Rulemaking
The NLRA, enacted in 1935, is the Federal statute that regulates most private sector labor-management relations in the United States.(1)    Section 7 of the NLRA, 29 U.S.C 157, guarantees that

                   Employees shall have the right to self-organization, to form, join, or assist labor organizations, to bargain collectively through representatives of their own choosing, and to engage in other concerted activities for the purpose of collective bargaining or other mutual aid or protection, and shall also have the right to refrain from any or all such activities[.]

In Section 1, 29 U.S.C. 151, Congress explained why it was necessary for those rights to be protected:

The denial by some employers of the right of employees to organize and the refusal by some employers to accept the procedure of collective bargaining lead to strikes and other forms of industrial strife or unrest, which have the intent or the necessary effect of burdening or obstructing commerce.

* * *
***** Experience has proved that protection by law of the right of employees to organize and bargain collectively safeguards commerce from injury, impairment, or interruption, and promotes the flow of commerce by removing certain recognized sources of industrial strife and unrest, by encouraging practices fundamental to the friendly adjustment of industrial disputes arising out of differences as to wages, hours, or other working conditions, and by restoring equality of bargaining power between employers and employees.
*****

It is declared to be the policy of the United States to eliminate the causes of certain substantial obstructions to the free flow of commerce and to mitigate and eliminate these obstructions when they have occurred by encouraging the practice and procedure of collective bargaining and by protecting the exercise by workers of full freedom of association, self- organization, and designation of representatives of their own choosing, for the purpose of negotiating the terms and conditions of their employment or other mutual aid or protection.

Complete text here: Notification of Employee Rights under the National Labor Relations Act.pdf.

(1) Labor-management relations in the railroad and airline industries are governed by the Railway Labor Act, 45 U.S.C. 151 et seq.