To me, this looks like something someone drew on vacation or a visit to Rome. It is a very impressive piece, but the 1920's was the era of modern art like cubism. Things like landscapes and scenery were really not of interest anymore.

People also used to be taught art extensively because cameras weren't widely owned. If you wanted to remember a place, you drew it.

It also does not seem to be signed. Most career artists signed their drawings or studies. For a buck you got yourself a great deal because this is a really cool piece and in amazing condition, but I honestly cannot think of many artists who were interested in scenery during this time period, other than Edward Hopper (who signed his drawings).

Your best bet would be to take it to an appraiser. I would go ahead and say it's worth more than a dollar, just because it is hand made and shows a piece of history, and therefor it is rare, but I'm not sure it's from any notable artist.