During which decade did federal support for child care significantly increase due to a demand for workers?

The 1940s saw a significant increase in federal support for child care, primarily driven by the demands of World War II. As many men were enlisted in the military and workforce shortages emerged, there was an urgent need for women to enter the workforce to fill these gaps. Recognizing this necessity, the government began to expand child care programs to support working mothers. This period marked a pivotal shift in the government's role in providing child care and laid the groundwork for future legislation aimed at enhancing child care resources and accessibility, continuing the trend into subsequent decades.

This context highlights why the 1940s was a critical decade for federal child care initiatives, making it the correct answer to the question about when federal support for child care significantly increased due to workforce demands.