Chester County (Pennsylvania Dutch: Tscheschter Kaundi), colloquially referred to as Chesco, is a county in the Commonwealth of Pennsylvania. It is located in the Delaware Valley region, located in the southeastern part of the state. As of the 2020 census, the population was 545,823(As of 2022),^[2] increasing by 7.1% from 498,886 in 2010.^[3] The county seat is the Borough of West Chester.^[4] The most populous of its 73 municipalities (cities, boroughs, and townships as defined at the state level) is Tredyffrin Township. The most populous boroughs are West Chester and Phoenixville. Coatesville is the only municipality in the County organized under the City form of government, a technical rather than demographic distinction. Chester County was one of the three original Pennsylvania counties created by William Penn in 1682. It was named for Chester, England. The county is part of the Southeast Pennsylvania region of the state.^{[lower-alpha 1]}

Quick Facts Country, State ...

Chester County
County
Chester County Courthouse
Flag Seal
Location within the U.S. state of Pennsylvania
Pennsylvania's location within the U.S.
Coordinates: 39.97°N 75.75°W / 39.97; -75.75
Country	United States
State	Pennsylvania
Founded	August 24, 1682
Named for	Chester, England
Seat	West Chester
Largest borough	West Chester
Government
• County commission	Josh Maxwell (D) Marian Moskowitz (D) Eric Roe (R)
Area
• Total	759 sq mi (1,970 km2)
• Land	751 sq mi (1,950 km2)
• Water	8.7 sq mi (23 km2)  1.1%
Population  (2020)
• Total	534,413
• Density	712.0/sq mi (274.9/km2)
Time zone	UTC−5 (Eastern)
• Summer (DST)	UTC−4 (EDT)
Congressional districts	5th, 6th
Website	www.chesco.org
Pennsylvania Historical Marker
Designated	October 26, 1982[1]

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Chester County is part of the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD Metropolitan Statistical Area. Along with southwest Delaware County, eastern Chester County is home to many communities that comprise part of the Philadelphia Main Line western suburbs of Philadelphia.

As of 2020, the county had the highest median household income level in Pennsylvania, and the 35th-highest in the nation.

Philadelphia, Bucks, and Chester were the three counties initially created by William Penn on August 24, 1682 in the colonial-era Province of Pennsylvania.^[5][6]

At the time, Chester County's borders were Philadelphia County to the north, the ill-defined western edge of the colony, located approximately at the Susquehanna River to the west, the Delaware River to the east, and Delaware and Maryland to the south. Chester County replaced the Pennsylvania portion of New Netherland's upland in New York, which was officially eliminated when Pennsylvania was chartered on March 4, 1681, and ceased existing in June of that year.^[7][8] Much of the Welsh Tract was in eastern Chester County, and Welsh place names, given by early settlers, continue to predominate there.

The fourth county in the state, Lancaster County, was formed from Chester County on May 10, 1729. On March 11, 1752, Berks County was formed from the northern section of Chester County and parts of Lancaster and Philadelphia counties.

The original Chester County seat was the City of Chester, a center of naval shipbuilding, at the eastern edge of the county. In an effort to accommodate the increased population of the western part of the county, the county seat was moved to a more central location in 1788; in order to mollify the eastern portion of the county, the village, known as Turk's Head, was renamed West Chester. In response to the new location of the county seat, the eastern portion of the county separated and formed the new Delaware County in 1789 with the City of Chester as its county seat.^[9]

Much of the history of Chester County arises from its location between Philadelphia and the Susquehanna River. The first "road to the West," a reference to Lancaster County, passed through the central part of Chester County, following the Great Valley westward; with some realignments, it became the Lincoln Highway and later U.S. Route 30. This road is still named Lancaster Avenue in most of the Chester County towns it runs through. The first railroad (which became the Pennsylvania Railroad) followed much the same route, and the Reading Railroad progressed up the Schuylkill River to Reading. Industry tended to concentrate along the rail lines. Easy transportation allowed workers to commute to urban jobs, and the rise of the suburbs followed. To this day, the developed areas form "fingers" extending along major lines of transportation.

During the American Revolutionary War, the Battle of Brandywine was fought in the southeastern part of the county. The Battle of the Clouds and the Battle of Paoli both took place in the northeastern part of the county, along with George Washington's encampment at Valley Forge.

According to the U.S. Census Bureau, the county has a total area of 759 square miles (1,970 km²), of which 751 square miles (1,950 km²) is land and 8.7 square miles (23 km²) (1.1%) is water.^[10] The topography consists of rolling hills and valleys and it is part of the region known as the Piedmont.

Watersheds that serve Chester County include the Octoraro, Brandywine, and Chester creeks, and the Schuylkill River. Many of the soils are fertile, rich loam as much as twenty-four inches thick; together with the temperate climate, this was long a major agricultural area.^[11] Because of its proximity to Philadelphia, Chester County has seen large waves of development over the past half-century due to suburbanization. Although development in Chester County has increased, agriculture is still a major part of the county's economy, and the number of horse farms is increasing in the county.^{[citation needed]} Mushroom growing is a specialty in the southern portion of the county.

Chester County is the only county to border both Delaware and Maryland.

Elevations (in feet): High point—1020 Welsh Mt., Honeybrook Twp. Other high points—960 Thomas Hill, Warwick Twp; 960 Barren Hill, West Caln Twp. Low point—66 Schuylkill River, Chester-Montgomery county line. Cities and boroughs: Coatesville 314; Downingtown 255; Kennett Square 300; Oxford 535; Parkesburg 542; Phoenixville 127; Spring City 114; West Chester 459.^[12]

Lanchester Landfill, located on the border of Chester and Lancaster Counties, captures methane which is sold for renewable natural gas credits, and piped to seven local businesses. This reduces the county's methane emissions, and provides an alternative to fracking for shale gas.^[13] In addition, several companies have their headquarters or a major presence in the county including Bentley Systems, EBS Healthcare, Main Line Health, Lavazza North America (formerly Mars Drinks), Depuy Synthes (part of Johnson & Johnson), Metabo, QVC, Hankin Group, Axalta Coating Systems, CTDI, Pactiv, Ricoh Americas, Blinding Edge Pictures, J.G. Wentworth, The Vanguard Group, and Victory Brewing Company among others.

As of the 2010 census, the county was 82.1% White Non-Hispanic, 6.1% Black or African American, 0.2% Native American or Alaskan Native, 3.9% Asian, 0.0% Native Hawaiian, 1.8% were two or more races, and 2.4% were some other race. 6.5% of the population were Hispanic or Latino.

As of the census^[18] of 2000, there were 433,501 people, 157,905 households, and 113,375 families residing in the county. The population density was 573 inhabitants per square mile (221/km²). There were 163,773 housing units at an average density of 217 units per square mile (84/km²). The racial makeup of the county was 89.21% White, 6.24% Black or African American, 0.15% Native American, 1.95% Asian, 0.03% Pacific Islander, 1.35% from other races, and 1.06% from two or more races. 3.72% of the population were Hispanic or Latino of any race. 18.0% were of Irish, 17.3% German, 13.1% Italian, 10.1% English and 5.6% American ancestry. 91.4% spoke English and 3.7% Spanish as their first language.

There were 157,905 households, out of which 35.10% had children under the age of 18 living with them, 60.50% were married couples living together, 8.10% had a female householder with no husband present, and 28.20% were non-families. 22.60% of all households were made up of individuals, and 7.60% had someone living alone who was 65 years of age or older. The average household size was 2.65 and the average family size was 3.15.

In the county, the population was spread out, with 26.20% under the age of 18, 7.90% from 18 to 24, 30.40% from 25 to 44, 23.80% from 45 to 64, and 11.70% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 96.40 males. For every 100 females age 18 and over, there were 93.10 males.

The median income for a household in the county was $65,295, and the median income for a family was $76,916 (these figures had risen to $80,818 and $97,894 respectively as of a 2007 estimate). Males had a median income of $51,223 versus $34,854 for females. The per capita income for the county was $31,627. About 3.10% of families and 5.20% of the population were below the poverty line, including 5.10% of those under age 18 and 5.50% of those age 65 or over.

The region was originally occupied by the Lenni Lenape people, who greeted European settlers in the seventeenth century with amity and kindness. British settlers were mostly English, Scotch-Irish and Welsh in ethnicity. From the late 19th to early 20th century, the industrial areas of the region, such as Coatesville, attracted immigrants and job seekers from Germany and Ireland, Eastern Europe, Italy, and the American rural South, with both black and white migrants coming north. Later Hispanic immigrants have included Puerto Ricans and, most recently, Mexicans.

Long a primarily rural area, Chester County is now ^[when?] the fastest-growing county in the Delaware Valley; it is one of the fastest growing in the entire Northeastern section of the United States.

Under Pennsylvania law, there are four types of incorporated municipalities: cities, boroughs, townships, and, in at most two cases, towns. The post office uses community names and boundaries that usually do not correspond to the townships, and usually only have the same names as the municipalities for the cities and boroughs. The names used by the post office are generally used by residents to describe where they live. The following cities, boroughs and townships are located in Chester County:

Chester County has four distinct seasons and has a hot-summer humid continental climate (Dfa) except for some far southern lowlands and areas along the Schuylkill River which have a humid subtropical climate (Cfa). The hardiness zone 7a except for 7b near the Brandywine Creek in Birmingham Township.

• Duffy's Cut
• National Register of Historic Places listings in Chester County, Pennsylvania