The yellow-dog contract was an anti-union device, used especially in the coal industry. It was a contract between employer and employee by which the employee agreed as a condition of employment not to join a labor union.

In West Virginia, blank copies of yellow-dog contracts were supplied to the coal operators by their regional operators associations in both long and short versions. In the contract the coal company stated that it would not knowingly employ any member of a labor union, and the miner agreed that (in the language of one such contract) he would not "become a member of, or connected or affiliated with, or aid, assist or encourage in any way, the United Mine Workers of America, the IWW or any other labor union."

After the 1917 U.S. Supreme Court decision in Hitchman Coal and Coke v. Mitchell, a case arising in West Virginia, yellow-dog contracts were viewed as legal and binding by state and federal courts. That changed when the right of workers "to organize and bargain collectively through representatives of their own choosing" was codified in 1933 in section 7a of the National Industrial Recovery Act and in 1935 in the Wagner Act, both acts of federal legislation.

The language of the NIRA specifically goes on to state "that no employee and no one seeking employment shall be required as a condition of employment to join any company union or to refrain from joining . . . a labor organization of his own choosing." The outlawing of this practice was one of the factors that allowed the miners union to organize the West Virginia coalfields in a very short time in the summer of 1933.