US Coast Guard and Geodetic Survey Seismological and Geomagnetic House, Scientific observation building in Sitka, United States.

The US Coast and Geodetic Survey Seismological and Geomagnetic House at 210 Seward Street is a 26-by-36-foot two-story wood-frame clapboard house with a gambrel roof, dormers on its east and west sides, and a full concrete basement set in bedrock. Its seven rooms comprise three bedrooms and a bathroom upstairs and, below, a kitchen, a living-dining room with a brick-chimney fireplace, and a former office-darkroom now holding a half bath. Covered porches measure 7 by 8 feet at the front and 4 by 4 feet at the back.

The house was built in summer 1916 by the US Coast and Geodetic Survey to house offices and living quarters for staff of the Sitka Magnetic Observatory, established in 1901 as Sitka's first permanent geomagnetic observatory. In 1922 cables linked the house to the observatory so staff could monitor its magnetometer from inside. In 1929 the observatory's seismometer, operating since 1904, was moved into the house's basement northwest corner. The observatory and seismometer left for a new site in 1940.

The house's alternative name, Forest Service House, comes from its 1961 transfer to the Department of Agriculture, which housed Tongass National Forest staff here. Before 1867 the lot held a public Russian Tea Garden. In 1986 the building was used as a medical educational facility.

The building sits on solid bedrock, which provides a stable foundation visible in its basement construction and important for understanding the site's scientific purpose. The location on Seward Street is easily accessible, and the exterior wood and roof details are clearly visible when walking past the structure.

The site was selected specifically because the absence of local magnetic disturbances allowed precise measurements of Earth's magnetic field. This geographical advantage made Sitka one of the few locations where such sensitive research could be conducted reliably during that era.