The Belfast Historic District encompasses a large portion of the city center of Belfast, Maine, representing one of Maine's largest concentrations of pre-Civil War architecture, as well as a rich collection of commercial architecture of the late 19th and early 20th centuries.

The city's downtown is organized as a series of roads paralleling the southern bank of the river, which is oriented roughly northwest to southeast.

The area extending from this point northward along Main Street contains a concentration of the city's finest late 19th-century commercial architecture, which is separately listed on the National Register as the Belfast Commercial Historic District, and includes as prominent landmarks the Belfast National Bank building and the former Masonic Temple.

It also includes major civic buildings: City Hall, the Waldo County Courthouse, and the Customhouse and Post Office, all built in the 1850s and designed by prominent architects.

[2] Extending south from this five-way intersection is Church Street, which is lined with a series of high-quality houses built primarily between 1840 and 1870.