These are supposedly futurist sketches drawn in 1929. However they lack the grandiose vision of such things, and several of them are clearly drawings of real objects that didn't exist until the 1930s or later: Hoover Dam, Shasta Dam, Grand Coulee Dam, the Oakland Bay Bridge, a P-38, a B-17, and UN Headquarters.
However, some of the drawings have a fanciful quality to them.
Others have a touch of Gotham City.
Others are just very well executed drawings of everyday stuff.