known as Greenville. Situated near Lancaster Ave., Powelton Ave., and Market St., Greenville served as a waypoint for travelers and cattle drivers, and many taverns and inns were established. Later, the area expanded in all directions with many German immigrants and offered much more than simple taverns. By the mid-20th century, the Greenville area had changed again, to a neighborhood that was colloquially referred to as the Black Bottom, signifying the neighborhood's racial and economic status. Much of this neighborhood was destroyed as part of a gentrification plan in the 1960s. The arrival of electrified streetcars in the 1890s kick-started development to the west of 43rd Street, and bridges and a tunnel in the first decade of the 20th century allowed people to easily commute into Center City. This led to rapid development within the borders of University City and far beyond. It was around this time that the "local" neighborhood names like Spruce Hill and Cedar Park were established. In the mid-1950s, two realtors and Penn graduates coined the name "University City" in an attempt to attract Penn faculty back to the neighborhoods near Penn. The boundaries were defined as extending from the "Schuylkill River to 52nd Street, and from Haverford Avenue to the Media-line railroad tracks south of Kingsessing Avenue — though over the years many have viewed it as a smaller domain". This has led to some community tension; some saw it as an attempt to secede from West Philadelphia. Boundaries University City's boundaries, as defined by the non-profit University City District organization and the City of Philadelphia, are the Schuylkill River to the east; Spring Garden Street, Powelton Avenue, and Market Street to the north; 52nd Street to the west; and Woodland Avenue, University Avenue, and Civic Center Boulevard to the south. Within these boundaries are the local neighborhoods of Cedar Park, Garden Court, Spruce Hill, Squirrel Hill, Powelton Village, Walnut Hill, and Woodland Terrace. The boundaries also encompass several historic districts, including the West Philadelphia Streetcar Suburb Historic District, and the ZIP codes 19104, 19139, and 19143. Town–university relations University City has a history of strained town and gown relations, particularly with the University of Pennsylvania ("Penn" for short), the city's largest private employer and the second-largest private employer in Pennsylvania. During the 1960s, Penn led a series of gentrification and redevelopment programs that have changed the character of the area. Opened in 2001, the