Monmouth Park originally opened on July 30, 1870. The track, which was planned by New York businessman John F. Chamberlain, New Jersey Senate President Amos Robbins and Adams Express Company President John Hoey, was intended to increase summer business for the local community of Ocean Port, New Jersey. Monmouth Park was very popular but closed after just three years due to financial difficulties. Four years later, however, the park reopened after its successful rehabilitation by a group of businessmen.
The rebuilt Monmouth Park opened its gates in 1882, and again became a popular summer getaway location. In 1890, a new racecourse was built adjacent to the existing track, and in 1890, the second Monmouth Park opened. However, the course closed in 1894 after state legislation passed that banned wagering on horse racing.
During the 1940s, successful lobbying led by Amory Haskell overturned the 1894 legislation and legalized betting on horse racing. Consequently, after more than 50 years since it closed, Monmouth Park reopened in June 1946. The track's opening day attracted 18,724 in attendance. Haskell would later have a handicap named after him; as of 2015, it is still run in late July.
In 1986, the New Jersey Sports and Exposition Authority purchased Monmouth Park for approximately $45 million. As of 2015, the NJSEA remains the track's owner and operator.