The Union Hotel building stands atop a rise in the village of Cundy's Harbor, located near the southeastern tip of Sebascodegan Island, which forms the eastern part of the town of Harpswell.

The building, which looks like a large house, stands on the west side of Cundy's Harbor Road, just north of the village library.

The building trim is a vernacular Italianate style, with corner pilasters rising to a broad entablature, and deep eaves.

[2] The Union Hotel was built in 1862 by Daniel Weeks Simpson, a native of nearby Brunswick who married into a local family.

It is believed to be the oldest resort hotel building in the state; an earlier instance in Harpswell, built in 1835, was destroyed by fire in 1868.