Cathedral of the Immaculate Conception (Portland, Maine)

Construction began in 1866 under the supervision of New York architect Patrick Keely. Construction  was interrupted by Portland's great 1866 fire, and it was not completed until September 8, 1869.

The church is a masonry structure, built of red brick, with sandstone trim and a slate roof. The main façade has a central entrance recessed in a sandstone Gothic arch, with a large stained glass rose window above. The main tower rises to the right of the main entrance, with buttressed corners, narrow Gothic windows, and an octagonal spire. Windows on the side walls are also Gothic, with buttressing between. The secondary buildings all have stylistically similar Gothic features

The interior of the cathedral is 186 by 70 feet. The nave is 150 feet long, rises 70 feet, and holds almost 1,000 worshipers. The tallest of the cathedral's three steeples is, at 204 feet.

The cathedral has undergone restorations in 1921, 1969, and 2000. In 1985, it was added to the National Register of Historic Places.

The Cathedral of the Immaculate Conception is a historic cathedral in Portland, Maine which serves as seat of the Diocese of Portland. The church is an imposing Gothic Revival structure built in 1866–69. It was listed on the National Register of Historic Places in 1985 and Until 2023, it was the tallest building in Portland.