The town of Riverhead is in Suffolk County, New York, on the north shore of Long Island. The population was 33,506 at the 2010 census. The name signifies that the mouth of the Peconic River is in this town. Riverhead is the county seat of Suffolk County.
The town was created in 1792 as part of developing new jurisdictions after the American Revolution. The New York State Legislature divided it from the extant Southold, New York. Colonists had purchased the Southold land from the local Algonquian-speaking Native Americans in 1649. An additional portion was purchased from Col. William Smith and divided among settlers in 1742. The poor section of Southold, with no harbor and little commerce, the town was separated at the behest of its inhabitants, who "represented to the Legislature that their town is so long that it is very inconvenient for them to attend at town meetings, and also to transact the other necessary business of the said town, and have prayed that the same may be divided into two towns".
On March 13, 1792, the Legislature passed a bill splitting off this section under the name River Head. The new enclave's first town meeting was scheduled to be held April 3, 1792. River Head was named the county seat (called "county town" at the time), and its name was later combined as Riverhead. By 1902, its approximate population was 2,500.