The Town of Clarkstown was created by an act of the New York State Legislature on March 18, 1791, during George Washington's first term of office. Since Rockland County was not created until 1798, Clarkstown was first a Town in Orange County before it became a Town in Rockland County.

In 1791 the population of Clarkstown was under 2000. In 1950 Clarkstown's population was approximately 15,000. With the opening of the Tappen Zee Bridge in 1955, the Palisades Interstate Parkway, and the Garden State Parkway extension, Clarkstown rapidly grew in population during the 1950s, 1960s and 1970s. As of the year 2000 census, Clarkstown's population was 82,082. Clarkstown ranks 15th in population of New York State's 932 towns.

Clarkstown is governed by a Town Board consisting of a Supervisor and four Councilpersons, all of whom are elected at large. The Supervisor serves for a two-year term, and the councilpersons serve for four-year terms, with two members of the council up for election every time the Supervisor runs. Clarkstown's other Elected Officials include the Town Clerk (two-year term), the Receiver of Taxes (four-year term), the Highway Superintendent (two-year term), and four Town Justices (four-year terms). The Supervisor is the Chief Fiscal Officer of the Town, as well as a member of the legislative body. Each member of the Town Board (the four Councilpersons and the Supervisor) has one vote. The Supervisor does not possess a veto, so issues are decided by a majority vote of the Town Board.

Clarkstown is located 25 miles from midtown Manhattan, and New City is the seat of both Town Government and Rockland County Government. The Town encompasses approximately 41 square miles and includes the hamlets of Bardonia, Central Nyack, Congers, Nanuet, New City, Rockland Lake, Valley Cottage, West Nyack, all of the Village of Upper Nyack, and portions of the Villages of Nyack and Spring Valley. Clarkstown has almost 300 miles of roads, which are maintained by the Town's Highway Department, and an extensive park system that continues to expand as the Town acquires additional lands under the Open Space program.

Clarkstown has a full assessed valuation of over $11.1 billion, an AA financial rating by Standard and Poor's and an Aa3 rating by Moody's. The Town is presently ranked the second-safest place to live among 300 communities with populations topping 75,000 people by Morgan Quitno Press. The Town is serviced by its own 171 member police department which covers the entire Town with the exception of the Spring Valley portion.