Plymouth became a township of the first class in January 1922. Isaac J. Sheppard became township secretary from that time until his retirement in 1952. Under the new form of government the board changed from "road supervisors" to "Township Commissioners". In 1925, the Board of Health was organized. Plumbing inspection began in 1934. In 1939, Plymouth adopted a "modern" zoning ordinance. A building code ordinance was adopted. In 1947, the first subdivision ordinance was adopted. In 1952, the Township Planning Commission was created, and a Recreation Committee was established to study recreation needs. Plymouth Township adopted a Home Rule Charter in 1972. This allows a municipality to take any governmental or administrative actions it requires, unless such actions are prohibited by general laws of the Commonwealth. From as early as 1688, lime kilns have been a large, productive and profitable business there. The Plymouth Meeting Historic District, Alan West Corson Homestead, Plymouth Friends Meetinghouse, and Hovenden House, Barn and Abolition Hall were listed on the National Register of Historic Places in 1971. Plymouth Meeting is located primarily within Plymouth Township, with a smaller portion lying within Whitemarsh Township. According to the United States Census Bureau, the CDP has a total area of , all of it land. Plymouth Township is immediately adjacent to the Schuylkill River, but all river frontage is occupied by industry. Currently a bike trail is under development for river access. Interstate 476 and the Pennsylvania Turnpike pass through the township. The area is easily accessible to Interstate 76 and the "Main Line" points across the river. As of the 2010 census, the CDP was 82.2% Non-Hispanic White, 6.2% Black or African American, 8.4% Asian, 0.6% were Some Other Race, and 1.4% were two or more races. 2.1% of the population were of Hispanic or Latino ancestry. As of the census of 2000, 5,593 people, 2,215 households, and 1,557 families resided in the CDP. The population density was 1,478.8 people per square mile (571.3/km2) living in 2,285 housing units at an average density of 604.2/sq mi (233.4/km2). The racial makeup of the CDP was 89.34% White, 3.40% African American, 0.09% Native American, 0.29% Asian, 0.14% from other races, and 0.73% from two or more races.