It would depend a lot on where the restaurant was: in a Chinatown, serving mostly Chinese customers, or elsewhere, serving mostly white customers. The former would serve traditional (southern) Chinese restaurant food, typically including gourmet dishes such as bird's nest soup, shark fin, sea cucumber (which could be quite expensive) and a range of cheaper dishes, from roast pig, roast duck, roast chicken, etc. through to Chinese omelets, noodle soups, stirfries (meat with vegetables) and simple vegetable dishes.
The latter would usually serve a mix of Western and Chinese dishes, with the Chinese menu often prominently featuring chop suey. Chop suey was well-known and fashionable enough to appear on menus in non-Chinese restaurants (see the Ziegfeld’s Midnight Frolic menu at the last link below), and in some cases would be the only Chinese dish listed on the English-language part of the menu in some Chinese restaurants.
A selection of menus can be seen at
http://program.dh.ucla.edu/projects/2015/projectchopsuey/restaurants/index.html
https://lovemenuart.com/collections/harley-spiller-chinese-menu-collection (they sell prints of the menus, but have on-line previews)
