There's a load of stuff on the web about the company, including this history on Grafton's official website, this story about Grafton's blues fest, and a great collection of labels here, and the wiki article.
I just stumbled across some amazing South-eastern Wisconsin history the other day. Apparently, a key blues and jazz record label of the 1920's and 1930's was based out of, of all places, Grafton, Wisconsin! The company was originally based out of Port Washington as the Wisconsin Chair Company. After they branched out into making cases for Edison phonographs, they eventually decided to start pressing their own records, too. They disingenuously referred to the record studios as the New York Recording Laboratories, but they were really located first in Port Washington, then in Grafton. Their labels included Paramount and Broadway.