The Lockwood-Mathews Mansion Museum is regarded as one of the earliest and finest surviving Second Empire Style country houses ever built in the United States. The 62-room mansion was built by banker-railroad tycoon LeGrand Lockwood, who in 1864 began construction of his estate on the Norwalk River in Norwalk, Connecticut. Designed by European-trained, New York-based architect Detlef Lienau, the mansion, which was completed in 1868, is considered his most significant surviving work. American craftsmen, along with many immigrant artisans, were employed in the construction of the house.

Lockwood's financial reversals in 1869 and his untimely death in 1872 resulted in the loss of the estate, then known as "Elm Park" through foreclosure in 1874. The property was sold to Charles D. Mathews and his wife Rebecca in 1876. Mathews, a prominent importer, from Staten Island, New York, and his family, resided in the mansion until 1938. In 1941 the estate was sold to the City of Norwalk and designated a public park.

When the building was threatened with demolition in the 1950s, local preservationists succeded in saving the mansion and formed the Lockwood-Mathews Mansion Museum, Inc. Designated a National Historic Landmark in 1971, the structure serves as a valuable resource of 19th-century American history. The Museum's mission is to conserve the building while creating educational programs on the material, artistic and social culture of the Victorian era.