West Islip is located at 40°42′54″N 73°17′52″W (40.715008, -73.297746).
According to the United States Census Bureau, the CDP has a total area of 6.8 square miles (17.5 km2), of which 6.3 square miles (16.4 km2) is land and 0.42 square miles (1.1 km2), or 6.46%, is water.
Great South Bay, Jones Beach Island and Fire Island lie to the south. Babylon and North Babylon form the western border. Bay Shore lies to the east, and in the north West Islip borders on Deer Park and Brentwood. West Islip is 45 miles (72 km) east of Manhattan and 45 miles (72 km) west of Southampton, New York. West Islip's western boundary is a natural one formed by Sampawams Creek, Hawley's Lake, Deer Lake and Swan Creek.
The first people to settle in this area more than one thousand years ago were the Secatogue Indians. The unearthing of an Indian burial ground north of West Islip beach enabled historians to reconstruct a village of these Indians who lived along the edges of the Great South Bay, Sampawams Creek, Trues Creek and Willetts Creek.
One of the main Indian trails was Udall's Road which was the first road in Suffolk County to run north and south. It was named for the Richard Udall family who had an estate on South Country Road (now Montauk Highway).
In the early 17th century, the West Islip area came under the influence of the Dutch. In 1664 it came under English rule when the Duke of York claimed Long Island with the permission of King Charles II.
In 1692 this land was purchased by Thomas and William Willetts through an agreement with the Secatogue Indians. These settlers found the area well suited for farming and hunting and the many waterways abundant with fish and shellfish. Since the Willetts owned most of West Islip, additional families did not arrive until late in the 1770s when parcels of land were sold to others. The tax rolls of 1757 only listed Willetts.
During the 19th century, the community became a popular haven of wealthy estate owners. Among these were the Magoun, Udall, Gerek and Smith families. Farming, charcoal production, lumbering and fishing were the main occupations. In the mid-19th century, the completion of the Long Island Rail Road brought travelers to West Islip and helped make the La Grange Inn a popular attraction. The inn had been established in the mid-18th century by the Higbie family.
The first schoolhouse was started in 1835 and was located on South Country Road. One of the school's first teachers, G.M. Bishop, taught for 33 years and by 1872 had 64 students in his class.
West Islip's population continued to grow slowly, and the 1930 census recorded 734 residents. In the early part of the 20th century, many Ukrainian people settled in West Islip seeking refuge from political repression and economic hardships. Some worked as gardeners on the estates while others became farmers, land owners and owners of small businesses. The Ukrainian heritage is still part of the community.
From 1940 until 1970, West Islip experienced most of its population growth. It had become an attractive suburban home community with its own fire department, post office, public library and Good Samaritan Hospital. A short drive on the Robert Moses Causeway affords access to good fishing at the Captree Boat Basin and swimming at Robert Moses State Park. West Islip boasts its own beach and marina.
Today West Islip is situated on over 4,000 acres (16 km2) and approximately 28,000 residents make West Islip their home. Numerous community groups offer support services and cultural enrichment for its residents. In addition to the various clubs and organizations affiliated with its schools and churches, there are the Chamber of Commerce, West Islip Beautification Society, American Legion, the Chamber Orchestra Society, Youth Enrichment Services and the West Islip Fire Department. Every September the West Islip Bicentennial Committee sponsors a county fair.
As of the census of 2010, there were 28,335 people in 9,040 households in the CDP. The racial makeup of the CDP was 95.9% White, 1.7% Asian, 0.6% Black, 0.1% Native American, and 0.6% from other races, and 1.1% being multiracial.
There were 7,459 families, out of which 39.4% had children under the age of 18 living with them, 68.2% were married couples living together, 10.3% had a female householder with no husband present, and 17.5% were non-families. Nearly 11.4% of all households were made up of individuals, and 6.9% had someone living alone who was 65 years of age or older. The average household size was 3.09, and the average family size was 3.43.
In the CDP, the population was spread out, with 25.6% under the age of 18, 4.0% from 18 to 24, 31.8% from 25 to 44, 21.9% from 45 to 64, and 12.2% who were 65 years of age or older. The median age was 37 years.
The median income for a household in the CDP was $103,789, and the median income for a family was $117,451. Males had a median income of $75,868 versus $54,389 for females. The per capita income for the CDP was $38,933. About 2.9% of families and 3.4% of the population were below the poverty line, including 4.9% of those under age 18 and 4.3% of those age 65 or over.
Long Island Rail Road.
Long Island MacArthur AirportGood Samaritan Hospital Medical Center
Public school districts:West Islip School District
Private schools:St. John the Baptist Diocesan High School 
Our Lady of Lourdes School
Public libraries:West Islip Public Library
Children living in West Islip attend grades K-5 in one of the district's four elementary schools, and grades 6–8 in one of two middle schools. Elementary and middle schools in West Islip are assigned by demographics. Children in families living on the south side of the LIRR Babylon/Montauk branch tracks are assigned to either Bayview Elementary, or Paul J. Bellew Elementary. Children who live on the north side of the tracks attend either Manetuck Elementary, or Oquenock Elementary School. In 2012 the school district closed two elementary schools; Kirdahy (Captree) Elementary School and Westbrook Elementary School. North side junior high school students attend Udall Road Middle School, and those on the south side attend Beach Street Middle school. For high school all middle schoolers move up to West Islip High School (located at 1 Lions Path, off of Higbie Lane) for 9th grade through 12th grade graduation.
Flash-based internet cartoon series Homestar Runner references West Islip in the cartoon "old comics". An apparent West Islip resident e-mails Strong Bad, which results in the character mispronouncing the name of the town as "is-lip" rather than the common pronunciation "ice-lip". Strong Bad also parodies the name, imagining West Islip as a "British new wave band". A poster for the fictional band later appears in the character's video game, Strong Bad's Cool Game for Attractive People.
American Abstract Expressionist artist Robert Motherwell made many prints at ULAE located in West Islip. He named one print "West Islip" in tribute to the locale and the print shop where the edition was pulled.Matt Anderson, New Jersey Devils forward
A. J. Benza, gossip columnist and television host
Sal Caccavale, former MLS player for the New York Red Bulls
Anthony Casamento, World War II US Marine Corps Medal of Honor recipient
Jen Corey, Miss District of Columbia 2009
Kevin Cosgrove, victim of the September 11th terrorist attacks whose 9-1-1 call and last words were recorded
Thomas Joseph Downey, congressman from 1975 to 1993, West Islip High School Class of 1966
Edie Falco, actress best known for her role on the long-running hit TV series The Sopranos
Bob Keeshan (Captain Kangaroo), children's television host. At one point in the 1950s he was a member of the School Board.
Minor C. Keith, railroad, fruit and shipping magnate
Aidan Kelly (luger), 2014 USA Olympic Luge slider
Mike Komisarek, retired NHL player for the Toronto Maple Leafs
Rick Lazio, 1976 WIHS graduate, member of the U.S. House of Representatives from New York's 2nd congressional district, 1993–2001
Ken Marino, actor and comedian
Al Oerter, Olympic discus thrower. Prior to Mexico City Olympics in 1968 he lived in West Islip and would frequently work out at the high school field.
Jeff Olson, cowboy of the Village People; moved to West Islip when 6 months old
Ricky Roxburgh, Raised in West Islip. 1997 WIHS graduate. Screenwriter of animated feature film Saving Santa, DreamWorks' Dragons and Disney's Tangled Animated Series.
Pete Sell, UFC "Ultimate Fighting Championship" middleweight fighter born in West Islip
Gary Sullivan, professional soccer player
Brett Swenson, placekicker in the NFL (Indianapolis Colts) born and raised in West Islip
Bob Wenzel, CBS Sports analyst, graduate of West Islip High School
Boomer Esiason, former NFL football quarterback and current WFAN radio host of Boomer and Carton in the Morning was born in West Islip.
David Letterman owned a home south of Montauk Highway in West Islip in the 1970s-80s
Doris Burke, sideline reporter and color analyst for NBA on ESPN born in West Islip
Nick Tropeano, Major League Baseball pitcher for the Los Angeles Angels of Anaheim