Most of the post office works of art were funded under the Treasury Department's Section commissions. Those works that were created using TRAP funds are so indicated. Although the WPA funded the construction of post office buildings, the artwork was not WPA but was usually produced under the Section or TRAP programs. Unless indicated, works of art are located in the US Post Office building.

Source:
Democratic Vistas: Post Offices and Public Art in the New Deal
by Marlene Park & Gerald E. Markowitz