The county's name derives from "rocky land", as the area has been aptly described, largely due to the Hudson River Palisades.

The area that became Rockland County was originally inhabited by Algonquian-speaking Native Americans, including Munsees and Lenape.

In June 1664, the Berkeley-Carteret land grant established the colony of New Jersey, dividing present-day Rockland and Bergen Counties into separate political areas.

A number of unique, Dutch-style red sandstone houses still stand, and many place names in the county reveal their Dutch origin.

[7] The natural barrier of the Ramapo Mountains and the size of the county made carrying out governmental activities difficult.

At one point, two governments were active, one on each side of the Ramapo Mountains, so Rockland split off from Orange in 1798 to form its own county.

During the American Revolution, when control of the Hudson River was viewed by the British as strategic to dominating the American territories, Rockland saw skirmishes at Haverstraw, Nyack, and Piermont, and significant military engagements at the Battle of Stony Point, where General "Mad" Anthony Wayne earned his nickname.

Yet another important chapter in the story of the Revolution was written on May 5, 1783, when General Washington received Sir Guy Carleton at the DeWint House, where they discussed terms of a peace treaty.

Two days later, Washington visited Sir Guy aboard a British war vessel, H.M.S Perseverance, laying anchor in the Hudson.

Many unsuccessful efforts were made to turn much of the Hudson Highlands on the northern tip of the county into a forest preserve.

Union Pacific Railroad president E. H. Harriman, though, donated land and large sums of money for the purchase of properties in the area of Bear Mountain.

The institution gained national infamy in 1972, when an investigation by Geraldo Rivera revealed the patients there to have been housed in neglectful conditions.

Rockland remained semi-rural until the 1950s, when the Palisades Interstate Parkway, Tappan Zee Bridge,New York State Thruway, and other major transit arteries were built.

[13] The county's terrain ranges from 1,283 ft (391 m) ASL on Rockhouse Mountain (northwest of Lake Welch)[14] to approaching sea level along the Hudson River.

About 9% of residents reported speaking Spanish at home, 5% Yiddish, 3% French-based creole, 1.5% Italian, 1.3% Tagalog, 1.3% Hebrew, 1.2% French, and 1% Russian.

[29][30] The county is served by several major highways, including Interstate 87/287 (the New York Thruway), opening from Suffern to Yonkers in 1955.

The Palisades Interstate Parkway, a project of master planner Robert Moses, and built between 1947 and 1958, connects the county directly to the George Washington Bridge due south.

[34][35] The Erie Railroad ran train service on the Northern Branch through the southeastern corner of the county to Nyack up to 1966.

[36] NY Waterway operates a ferry service between Haverstraw and Ossining in Westchester County for the Metropolitan Transportation Authority.

Ferry service is typically suspended in the colder months when the Hudson River freezes over, and commuters must take shuttle buses across the Tappan Zee Bridge.

Generally, the Supreme Court in Rockland County hears civil cases involving claims in excess of $25,000.

Each of the towns and 15 of the villages have Justice Courts, which mostly hear routine traffic ticket cases, especially from the New York State Thruway and the Palisades Interstate Parkway.

[44] Like most of the Hudson Valley, Rockland County historically voted Republican but in recent years has leaned Democratic.

[55] Recent EPA statistics show that a total of 66 presently active Rockland County facilities are currently regulated.

From 2015 to 2018, the Haverstraw Quarry owned and managed by CRH Tilcon and Oldcastle Materials was heavily fined for air and water pollution, including over-blasting, over-excavating, non-viable use of its NESCO unhealthy dust suppression systems and lethal dust & water runoffs into protected waterways.

and New York State Department of Environmental Conservation (NYSDEC) Conservationfound/investigated and informed Suez of untreated polluted water at Tilcon operated discharge points at a stream that flows into Lake DeForest.

[68] News reports confirmed that the first known case of polio in the United States in a decade was discovered in Rockland County in July 2022.

[69][70] In 2014, Clarkstown created a first-of-its-kind in New York State 2.3-megawatt solar system consisting of about 4,300 panels on top of a closed, highly regulated, flat shadeless 13-acre section of the former garbage landfill in West Nyack.

The unit is sized to generate 3 million kilowatt-hours annually – enough power to supply about 200 homes, that provides one-third of the electric needs of the Town of Clarkstown government.

Clarkstown is divided into 4 wards[75] for the purposes of municipal representation Well-known residents of Rockland County have included: Burgess Meredith Don Costa Gary Chester Harold Coletta John Cage Nick Perito Sherwood Anderson