Whats the main difference (in appearance) between houses built in the 1940's and 1920's?

http://www.ragtime.org/arch/index.html

Although there aren’t a lot of pictures, the info seems to be pretty spot-on. On several levels, architecture mirrors art movements in other metiers, esp. in fine art.

I think another way to research this is to look into the urban planning for your region; if you are able to find out when neighborhoods were established, you can see a pretty clear pattern of representative styles for that era. Here in L.A., a city well known for its “sprawl” over the years/generations, you can see an interesting progression chronologically from the urban and suburban centers…my locale in Pasadena, Ca. has an pretty clear representation of this as many of the neighborhoods sprouted up post-World War II and were of the ranch/cottage style. Prior to that, a lot of Craftsman-style homes were set in what is now come to be known as the “California Bungalow” style.

p.s. Welcome to Fluther miranda!

Are you asking about houses in the USA or any where in particular?

The Prairie style, perhaps epitomized by F.L. Wright, was a popular style from the very late 1800s through the 1920s. The Prairie shared a lot of stylistic elements with the Craftsman style. Both contributed elements to the Ranch style, which really took off right after WWII when the millions of soldiers returned home and started families.

You can occasionally see some influences from the International movement in houses of these periods, but that style was (and still is) a bit “controversial” for the tastes of middle Americans.