The most significant piece of legislation during the New Deal era of Franklin D. Roosevelt would be the National Labor Relations Act, sometimes referred to as the Wagner Labor Relations Act.
Passed in 1935, this law guaranteed the right of groups of workers, through representatives, to negotiatecontracts with management. For the first time in the history of the United States, workers had a right to collectively bargain.
In the past, government had aggressively come down on the side of corporate owners, often using police or even military troops to break strikes and arrest protesters. The government also looked the other way when private strikebreakers, part of the Pinkerton Agency, were hired to come in and challenge unions. Deaths were often the result and little or no action was ever taken.
Now, with Wagner, a National Labor Relations Board was created. If management refused to negotiate with the workers, a federal arbitrator could be called in to write the contract for them, which was never in favor of management. This gave owners a powerful incentive to sit down at the table with organized labor.
The other result of this law was that union membership increased several fold, and organizers could come out of the shadows. The Congress of Industrial Organizations (CIO) was formed at this time and immediately recruited hundreds of thousands of members, as did the International Brotherhood of Teamsters.