I have a book somewhere, published in 1974, which details this. You had the City of Anchorage, with police powers citywide, whose corporate limits stretched south to between Fireweed and near Tudor depending on exactly where, and east to between near Boniface and Patterson depending on exactly where. The borough had the "Spenard Police Service Area", which stretched south from city limits to Dowling or pretty close, extending to around 68th along the Lake Otis and Old Seward corridors. Both areas excluded Muldoon Road. The borough contracted with APD to provide service to its police service area, which provided some measure of consistency, but still there were different laws. When unification occurred, both areas formed the core of the municipality's police service area, which expanded over time. The current boundaries date mostly to the early 1990s and the protracted, controversial issue of annexing Basher and the Hillside, also in response to AST's threats to pull out of those areas.