Monmouth County () is a county located in the central portion of the U.S. state of New Jersey. It is bordered to its west by Mercer and Middlesex Counties, to its south by Ocean County, to its east by the Atlantic Ocean, and to its north by the Raritan Bay (sharing a border with the boroughs of Staten Island, Brooklyn, and Queens in New York City, across it). Monmouth County's geographic area comprises 30% water. The county forms part of the New York metropolitan area. Monmouth County calls itself The Place You Want to Be. The county is part of the Jersey Shore region of the state."Regions: North, Central, South, Shore - Best of NJ", Best of NJ, Accessed May 30, 2024. "Atlantic, Cape May, Monmouth, and Ocean County make up the Jersey Shore region."

As of the 2020 United States census, the county was the state's fifth-most-populous countyTable1. New Jersey Counties and Most Populous Cities and Townships: 2020 and 2010 Censuses, New Jersey Department of Labor and Workforce Development. Accessed December 1, 2022. with a population of 643,615, its highest decennial count ever and an increase of 13,235 (+2.1%) from the 2010 census count of 630,380, which in turn reflected an increase of 15,079 from 615,301 at the 2000 census., United States Census Bureau. Accessed January 22, 2013. As of 2010, the county fell to the fifth-most populous county in the state, having been surpassed by Hudson County.NJ Labor Market Views , New Jersey Department of Labor and Workforce Development, March 15, 2011. Accessed October 7, 2013. The United States Census Bureau's Population Estimates Program estimated a 2025 population of 651,035, an increase of 7,420 (+1.2%) from the 2020 decennial census.

Monmouth's county seat is Freehold Borough,New Jersey County Map , New Jersey Department of State. Accessed July 10, 2017. though many county offices are also located in neighboring Freehold Township. The most populous place was Middletown Township, with 67,106 residents at the time of the 2020 Census, while Howell Township covered , the largest total area of any municipality.

While there are differing historical theories, the most plausible of theories in the origin of the county's name are attributed to many settlers originating from Rhode Island where the Rhode Island Monmouth Society hailed from, or it being named after the historic county of Monmouthshire in Wales, Great Britain. The county, like much of the state, was significantly involved during the American Revolutionary War. The Battle of Monmouth was fought in June 1778 in what has been preserved as Monmouth Battlefield State Park, currently located in Freehold Township and Manalapan Township.Monmouth Battlefield State Park , New Jersey Department of Environmental Protection Division of Parks and Forestry. Accessed February 3, 2024.

The county's economy is rich and diverse, due to its high population density and proximity to New York City. Located in the middle of the Northeast megalopolis, its inland county seat of Freehold Borough, the Tri-City region of coastal cities of Red Bank, Long Branch, and Asbury Park, along with the county constituting a vast swath of the New Jersey coastline, has contributed in its draw of tourists throughout the state (and much of the Northeastern United States at large), particularly during the summer months., tri CityNews. Accessed February 3, 2024. Many communities within the county serve as commuter towns to and from New York City and other points north. Highways such as the Garden State Parkway, U.S. 9, Routes 34, 35, and 36, along with NJ Transit's North Jersey Coast Line and Seastreak, connects county residents to economic centers in North Jersey and New York City. In 2015, the county had a per capita personal income of $69,410, making it the fifth highest in New Jersey and ranked 74th of 3,113 counties in the United States.250 Highest Per Capita Personal Incomes available for 3113 counties in the United States: 2015 , New Jersey Department of Labor and Workforce Development. Accessed February 4, 2024.Local Area Personal Income: 2015 , Bureau of Economic Analysis. Accessed February 3, 2024. Many inland areas of the county are still quite agricultural, with many orchards, wineries, equestrian farms, and distilleries, such as Cream Ridge Winery, Delicious Orchards, Four JG's Orchards & Vineyards, and Laird & Company. The Bell Labs Complex is a major scientific research facility in Holmdel Township, where important breakthroughs, such as evidence for the Big Bang, were discovered.Penzias and Wilson discover cosmic microwave radiation - 1965 PBS. Accessed February 3, 2024. "Bell Labs built a giant antenna in Holmdel, New Jersey, in 1960. It was part of a very early satellite transmission system called Echo.... Since Penzias, Wilson, and Dicke's work, all that has changed. The measurement of cosmic background radiation (as the Holmdel telescope's noise is now called), combined with Edwin Hubble's much earlier finding that the galaxies are rushing away, makes a strong case for the big bang. By the mid 1970s, astronomers called it 'the standard model.' Arno Penzias and Robert Wilson received the Nobel Prize in physics in 1978." The county is also home to Monmouth University, a private university in West Long Branch.

History

Etymology The naming of Monmouth County has different historical theories. It is thought that the county received its name from the Rhode Island Monmouth Society.The Origin of New Jersey Place Names: M, GetNJ.com. Accessed December 15, 2007.Lippincott III, Bertram. "The Rhode Island Settlers of Monmouth County, New Jersey", Newport History, Vol. 71 : Issue 247, Article 3. Accessed March 18, 2022. "However, in 1664, about eighty first and second generation Rhode Island settlers were responsible for the establishment and growth of Monmouth County in the Province of East Jersey. The reasons for the settlement of Monmouth County by Rhode Islanders are tied to the mobility of its early settlers and their persistent desire to seek land, opportunity, and freedom of worship." This is likely, due to many of the county's earliest settlers originating from Rhode Island. Another plausible theory is from a suggestion from Colonel Lewis Morris that the county should be named after Monmouthshire in Wales, Great Britain. Other suggestions include that it was named for James Scott, 1st Duke of Monmouth (1649–1685), who had many allies among the East Jersey leadership.How Monmouth County Got Its Name , Monmouth County, New Jersey. Accessed August 14, 2008.

Indigenous history

Around the year 1000, the area of Monmouth County began to be inhabited by the Lenape Native Americans prior to the arrival of European settlers. They came from the Mississippi River area. They lived along the vicinity of the Jersey Shore, the Raritan Bay, the Raritan River and other areas in the northeastern United States. The Lenape were a hunter-gatherer society. They were largely sedentary, changing campsites seasonally. They were prolific hunters of small game and birds. They were also skilled fisherman, and were known to harvest vast amounts of clams from the bays and inlets on the Jersey Shore. They also practiced some agriculture to augment their food supply. During this time, an important crossroad of two major Lenape trails was located in the area of Freehold Township in western Monmouth County.Pepe, p. 19.

Colonial era

In 1609, the English navigator, Henry Hudson, and his crew aboard the Dutch vessel Half Moon spotted land in what is now Monmouth County, most likely off Sandy Hook; however, some historical accounts credit this landing to present-day Keansburg. Among the first European settlers and majority landowners in the area were Richard and Penelope Stout. Penelope "miraculously" survived her wounds from a native attack in Sandy Hook and lived to the age of 110. A group of Quaker families from Long Island settled the Monmouth Tract, an early land grant from Richard Nicolls issued in 1665. They were followed by a group of Scottish settlers who inhabited Freehold Township in about 1682-1685, followed several years later by Dutch settlers.. As they arrived in this area, they were greeted by Lenape people, who lived in scattered small family bands and developed a largely amicable relationship with the new arrivals.Freehold Township , Monmouth County, New Jersey. Accessed July 12, 2012. Enslaved Africans were present in the area from at least 1680, and by 1726 made up 9% of the total population of the county.Hodges, Graham Russell. Slavery and Freedom in the Rural North: African Americans in Monmouth County, New Jersey, 1665–1865, p. 32. Madison, WI: Madison House, 1997. . Accessed October 7, 2013.

Monmouth County was established on March 7, 1683, while part of the province of East Jersey. On October 31, 1693, the county was partitioned into the townships of Freehold, Middletown and Shrewsbury.Snyder, John P. The Story of New Jersey's Civil Boundaries: 1606-1968 , Bureau of Geology and Topography; Trenton, New Jersey; 1969. p. 177. Accessed October 1, 2013.

Since June 1764, the Sandy Hook Light has guided ships safely into New York Harbor, making it the nation's oldest operating lighthouse.Sandy Hook Lighthouse, National Park Service. Accessed March 16, 2026. "The Sandy Hook Lighthouse is the oldest operating lighthouse in the nation. The lighthouse was completed on June 11, 1764 due to the efforts of 43 prominent New York merchants. The merchants petitioned the Colonial Assembly of New York to request that a lighthouse be erected on Sandy Hook to guide ships safely into New York Harbor." The light was designated as a National Historical Landmark in 1964, marking 200 years since it first went into use."Sandy Hook Light Now an Official U.S. Landmark; Sandy Hook Light Made U.S. Shrine; 200‐Year‐Old Jersey Tower Is Dedicated as National Historic Landmark", The New York Times, June 12, 1964. Accessed March 16, 2026. "Sandy Hook Light was dedicated as an official National Historic Landmark today on the 200th anniversary of the date it began operating. The light is an 85-foot‐tall, hexagonal‐shaped white tower that still provides a reference point for navigators entering and leaving New York Harbor. Its construction was begun in 1762 and was completed two years later."

At the June 28, 1778, Battle of Monmouth, near Freehold Township, General George Washington's soldiers battled the British under Sir Henry Clinton, in the longest land battle of the American Revolutionary War. At Monmouth the tactics and training from Friedrich Wilhelm von Steuben developed at Valley Forge during the winter encampment were first implemented on a large scale.Capuzzo, Jill P. "British Beware: Monmouth Redux" , The New York Times, May 18, 2003. Accessed April 9, 2012. "The largest land artillery battle of the Revolutionary War, the Battle of Monmouth marked a significant turning point in the colonies' fight against the British crown." Other battles and massacres during the war in Monmouth County include sites such as the Burrowes Mansion in Matawan, and the Allen House in Shrewsbury.

At independence, Monmouth's population included 1,640 slaves, as well as an undetermined number of free African Americans. The number of enslaved persons fell steeply after 1820, though a small number remained until at least 1850. Monmouth's free African American population climbed from 353 in 1790 to 2,658 in 1860. There was a small African-American middle class consisting of freedmen present in Monmouth County by the 1840s and 1850s.New Jersey: A History of the Garden State edited by Maxine N. Lurie, Richard F. Veit page 131