Merritt was elected as a Democrat to the Forty-second Congress (March 4, 1871 – March 3, 1873); he was an unsuccessful candidate for renomination in 1872. He moved to Salt Lake City, Utah in 1873 and engaged in mining operations and the practice of law. He was city attorney 1888–1890, and served as a member of the Democratic National Committee in 1892. He was chief justice of the supreme court of the Territory of Utah from 1894 to 1896. He died in Salt Lake City at age 83, and was interred in Salt Lake City Cemetery.