In conjunction with GL's 72nd Anniversary, Mo asks below: When did the Bauers arrive on the scene and the town name change to Springfield?
In July of 1948, a woman calling herself Jan Carter arrived in Selby Flats (the show's second location after Five Points). She was really Meta Bauer -- although the family's original name was Baum. Creater Irna Phillips changed her mind after a few scripts. On August 31, 1948, Papa Bauer made his first appearance. Daughter Trudy and son Bill followed soon after.
In 1966, Bill Bauer transferred to the Springfield office of his public relations firm, taking his family with him. Coincidentally, family friend Dr. Paul Fletcher became Chief of Staff at Cedars Hospital located in the same city and also brought his family along. In fact, it seemed like the only former resident of Selby Flats not making the move to Springfield was Bill and Bert's son, Mike. Along with his young daughter, Hope, Mike also moved to the Midwest... but to the town of Bay City (he and Hope moved to Springfield in 1968).
Hope this answers your question, Mo!