The Merchant's House Museum, also known as the Old Merchant's House and the Seabury Tredwell House, is a historic house museum at 29 East Fourth Street in the NoHo neighborhood of Manhattan in New York City. Built by the hatter Joseph Brewster in 1831 and 1832, the edifice is a four-story building with a Federal-style brick facade and a Greek Revival interior. It was the Tredwell family's residence for almost a century before becoming a museum in 1936. The Merchant's House Museum is the only 19th-century residence in Manhattan with its original exterior and interior intact.

Brewster built the house as a speculative development, selling it in 1835 to the merchant Seabury Tredwell, who lived there with his family and servants. The structure remained in the family until the death of the youngest child, Gertrude, in 1933. George Chapman, a distant relative, purchased the building and transformed it into a museum. Over the next three decades, the museum's operators struggled to obtain funds to restore the deteriorating house. The architect Joseph Roberto completely renovated the building from 1970 to 1980, and the museum underwent further restoration in the early 1990s after the demolition of nearby buildings damaged it. During the 2010s and 2020s, museum officials protested the construction of a nearby hotel because of concerns that the project would further damage the house.

The Merchant's House Museum has a raised basement, a front doorway accessed by a stoop, a slate roof, and a rear garden. The interior consists of a family room and kitchen in the basement; two parlors on the first floor; and bedrooms on the upper floors. The museum's collection has over 4,500 items owned by the Tredwell family, including pieces of furniture, clothing, household items, and personal items. The museum also hosts various performances and events, and it operates tours and educational programs. Reviewers have praised both the museum's exhibits and the architecture. The building's facade and interior are New York City designated landmarks, and the building is a National Historic Landmark.

The Merchant's House Museum, originally the Seabury Tredwell House, is at 29 East Fourth Street in the NoHo neighborhood of Manhattan in New York City. It is on the north side of Fourth Street, between Lafayette Street to the west and Bowery to the east. The land lot is rectangular and measures 3,072 square feet (285 m²), with a frontage of 24.25 feet (7.39 m); the lot extends 128.83 feet (39.27 m) back from the street. The current museum was built as one of six identical houses on the same block.

Abutting the museum to the east is a public park named Manuel Plaza. Built atop a construction shaft for New York City Water Tunnel No. 3, it was named in honor of five African-born slaves who received land in the neighborhood from the Dutch West India Company. Several doors east of the museum, at 37 East Fourth Street, is the Samuel Tredwell Skidmore House, a three-story Greek Revival house built for a cousin of one of 29 East Fourth Street's early residents, Seabury Tredwell. The De Vinne Press Building to the west and the Astor Library (also known as the Public Theater) to the north are on the same block. Other nearby buildings include the Firehouse of Engine Company No. 33 one block south, 357 Bowery half a block east, and the Schermerhorn Building half a block west.

The site was formerly part of the estate of German-American businessman John Jacob Astor, who, in 1803, acquired land between what is now Astor Place and Great Jones Street. Astor subsequently built his mansion and horse stable directly to the west of the Seabury Tredwell House. In the 1830s, the wealthiest New Yorkers were starting to relocate northward from what is now the Financial District of Manhattan to what is now Lafayette Street in NoHo. At the time, the area surrounding Lafayette Street was still mostly undeveloped. Residential development in the area peaked at that time before moving northward again in the 1840s and 1850s.

The house was first occupied by Seabury Tredwell, a merchant born in 1780 to a prominent Long Island family; he was a descendant of Samuel Seabury, an Episcopal bishop. Tredwell established a business on Pearl Street in Lower Manhattan around 1803 or 1804, which later became Tredwell, Kissam & Company. Tredwell married Eliza Parker in 1820, and the couple had seven children over the next fifteen years, before Tredwell retired in 1835. Although Tredwell had been a successful businessman during his career, he was not well known outside of his community.

Joseph Brewster, a hatter who also developed speculative real estate projects, acquired two land lots in 1831 for a combined $6,550 (equivalent to $193,000 in 2024). On one of these land lots, he built a townhouse at 29 East Fourth Street. Brewster built five additional houses on the same street. Brewster finished 29 East Fourth Street in April 1832 and lived there for three years. Brewster sold the building in 1835 to Tredwell for $18,000 (equivalent to $549,000 in 2024). It remained the Tredwell family's residence for nearly a century. They vacationed in New Jersey during the summer but lived on Fourth Street the remainder of the time, shunning publicity. Tredwell's youngest daughter, Gertrude, was born in the house in 1840. Gertrude, her two brothers, and her five sisters all lived there with their parents.