According to the Lilly Library at the University of Indiana: "...Headed by Harry L. Hopkins and supplied with an initial congressional appropriation of $4.880 billion, [the WPA] offered work to the unemployed on an unprecedented scale by spending money on a wide variety of programs, including highways and building construction, slum clearance, reforestation, and rural rehabilitation. So gigantic an undertaking was inevitably attended by confusion, waste, and political favoritism, yet the 'pump-priming' effect stimulated private business during the Depression years and inaugurated reforms that states had been unable to subsidize.
"Particularly novel were the special programs. The Federal Writers' Project prepared state and regional guide books, organized archives, indexed newspapers, and conducted useful sociological and historical investigations. The Federal Arts Project gave unemployed artists the opportunity to decorate hundreds of post offices, schools, and other public buildings with murals, canvases, and sculptures; musicians organized symphony orchestras and community singing. The Federal Theatre Project experimented with untried modes, and scores of stock companies toured the country with repertories of old and new plays, thus bringing drama to communities where it had been known only through the radio.
"By March, 1936, the WPA rolls had reached a total of more than 3,400,000 persons; after initial cuts in June 1939, it averaged 2,300,000 monthly; and by June 30, 1943, when it was officially terminated, the WPA had employed more than 8,500,000 different persons on 1,410,000 individual projects, and had spent about $11 billion. During its 8-year history, the WPA built 651,087 miles of highways, roads, and streets; and constructed, repaired, or improved 124,031 bridges, 125,110 public buildings, 8,192 parks, and 853 airport landing fields."
An initial appropriation of $4.88 billion sounds like ordinary federal spending, but translated into 2007 dollars it would be $73.2 billion -- it was a massive program indeed. There had been predecessor relief programs both under Hoover and then FDR, but nothing on this scale.