Formally established as a Township is 1692, Middletown Township came into existence ten years earlier when William Penn and his surveyor, General Thomas Holme, laid out the City of Philadelphia. Bucks County was divided into five townships: Middletown, Makefield (now Upper and Lower Makefield), Buckingham (now Bristol Borough and Bristol Township), Falls, and Salem (now Bensalem). Middletown got its name for being the geographic center of the five townships. The present-day boroughs of Langhorne, Langhorne Manor, Hulmeville, and Penndel were part of Middletown Township until the late 1800s. The succession of the four boroughs gave the Township is current, unique boundary.
Swedish and Dutch immigrants were the first to settle the Township, and they were closely followed by English, Welsh, Quaker, Scottish, and Irish immigrants. The early Dutch settlers mimicked Native American methods to plant sycamore trees near water sources, and a few of these 17th-century trees still stand to this day along a tributary feeding the Neshaminy Creek. Early settlements in Langhorne Terrance and Parkland developed as summer home communities, and other areas developed along transportation routes. Attleboro, Middletown’s largest urban development in the early 1700s, was founded along a railroad line that operates today as the Southeastern Pennsylvania Transportation Authority's (SEPTA) West Trenton Line. Attleboro was renamed Langhorne in 1876 in honor of former Pennsylvania Supreme Court Chief Justice Jeremiah Langhorne, an early resident of the area.
Much of the Township remained a farming community until the late 1800s. Development of the rail line from Philadelphia, and the later invention of the automobile, led to a wave of Philadelphians migrating from the city to the more rural region. As Langhorne’s growth slowed after World War I, the lower portion of the Township took off after World War II. The largest expansion came in the late 1950s when William Levitt built Levittown, the second of his developments (the first was on Long Island, New York). When completed in 1958, it was the largest suburban planned community in the United States. Its unique alphabetized street name sections still exist today. Levittown is now considered one of the largest suburbs of Philadelphia, and it is governed by Middletown as well as three neighboring municipalities.
Residential and commercial development continued from the 1950s to the present day, making for considerable growth to the Township. One of the most significant commercial developments was the construction of the Oxford Valley Mall in 1973. Sesame Place opened in 1980 and immediately became a national family attraction. Both of these sites still feature as prominent landmarks in the Township today. The Township is home to approximately 120 historically significant sites, many dating back to the Civil War Era. These include stops for runaway slaves fleeing north along the Underground Railroad. Attleboro was home to one of the first free black communities in Bucks County.
Middletown was also home to the former Langhorne Speedway, one of the most feared racetracks that operated between 1921 and 1971. Despite hosting NASCAR races in its heyday during the 1950s, it remained unpopular with drivers due to its difficulty and danger – 27 people lost their lives on the track. Shortly after closing, the property was developed into a shopping center and has since been designated as a historical site.