The Bangor Historical Society operates out of the Thomas A. Hill House on Union Street, a beautifully preserved Federal-style mansion from the 1830s. Inside, the society maintains exhibits on Bangor's history — the lumber boom, the city's maritime past, and the Victorian era when Bangor was one of the wealthiest cities per capita in the United States.
The society offers the Best of Bangor Walking Tour, a guided walk through the downtown historic district that covers the lumber-baron mansions, the old commercial waterfront, and the key sites of 19th-century Bangor. They also run guided tours of Mount Hope Cemetery in summer. Both tours are worth doing before exploring the city on your own — the context helps enormously when you're looking at buildings that otherwise just seem old.