This topic seems like it might be a lot of fun. There are amusement parks all over the world and I'm sure they show up on a lot of postcards. Many early parks started out as bath houses, such as Cedar Point in Sandusky, Ohio. I have a couple foldout cards from when it was primarily a lakeside resort. By the 1920s, the park had a roller coaster and several other rides. One of these wooden coasters is still in operation after more than a century.
The White City Amusement Park in Chicago was built on the remains of the 1893 Columbian Exposition. I'm not sure how long it lasted.
Coney Island is, of course, still going strong. Luna Park was one of three amusement parks that were running at its peak. It was destroyed in a fire in 1944.
Oaks Park in Portland, OR is is one of the oldest amusement parks still in operation, though relatively small by Six Flags standards. The Chutes are gone, but the grand wooden roller rink is still around, along with the 1913 carousel.
Bath houses up next ...