The WPA was built to give jobs, but it hired cooks, nurses, teachers and librarians off the relief rolls and put them to work at what they knew. The result was an unplanned welfare agency: roughly half a billion hot school lunches, nursery schools, public-health nursing, literacy classes and bookmobiles. The school lunch became permanent in 1946.
Calling the WPA the first national welfare agency is a framing, since it delivered services as a byproduct of work relief. The 1946 school lunch law also grew from surplus-disposal and wartime nutrition concerns, so the WPA is a principal ancestor, not the sole cause.