Lock Haven, Pennsylvania

===20th century ===
[[File:PostcardBirdsEyeViewLockHavenPa1911.jpg|thumb|alt=A tinted postcard depicts a town as seen from a hillside. It is laid out on a triangle of flat land between two converging streams. The larger and more distant of the two streams is flowing from mountains, while the smaller stream flows through farmland.|An aerial postcard illustration of Lock Haven with Bald Eagle Creek (in foreground) and the West Branch Susquehanna River (in background) in 1911]]
[[File:Piper Aviation Museum 2.jpg|thumb|Piper Aviation Museum|alt=A white van is parked in front of a rectangular three-story building with many windows. A sign on the building says, "Piper Aviation Museum".]]
[[File:Pennsylvania - Lewisburg through Marcus Hook - NARA - 68148320 (cropped).jpg|thumb|right|Lock Haven in 1930]]
As older forms of transportation such as the canal boat disappeared, new forms arose. One of these, the [[tram|electric trolley]], began operation in Lock Haven in 1894. The Lock Haven Electric Railway, managed by the Lock Haven Traction Company and after 1900 by the Susquehanna Traction Company, ran passenger trolleys between Lock Haven and [[Mill Hall, Pennsylvania|Mill Hall]], about {{convert|3|mi|km|0}} to the west. The trolley line extended from the [[Philadelphia and Erie Railroad]] station in Lock Haven to a station of the [[Central Railroad of Pennsylvania (1891–1918)|Central Railroad of Pennsylvania]], which served Mill Hall. The route went through Lock Haven's downtown, close to the Normal School, across town to the trolley car barn on the southwest edge of the city, through Flemington, over the Bald Eagle Canal and Bald Eagle Creek, and on to Mill Hall via what was then known as the Lock Haven, Bellefonte, and [[Nittany Valley]] Turnpike. Plans to extend the line from Mill Hall to Salona, {{convert|3|mi|km|0}} south of Mill Hall, and to [[Avis, Pennsylvania|Avis]] {{convert|10|mi|km|0}} northeast of Lock Haven, were never carried out, and the line remained unconnected to other trolley lines. The system, always financially marginal, declined after [[World War I]]. Losing business to automobiles and buses, it ceased operations around 1930.{{sfn|Shieck|Cox|1978|pp=81–92}}

[[William T. Piper Sr.]] built the [[Piper Aircraft]] Corporation factory in Lock Haven in 1937 after the company's Taylor Aircraft manufacturing plant in [[Bradford, Pennsylvania]], was destroyed by fire. The factory began operations in a building that once housed a silk mill.<ref name=plan>{{cite web |author=City of Lock Haven Planning Office |author2=Clinton County Comprehensive Planning Advisory Committee |author3=Gannett Fleming, Inc. |author4=Larson Design Group | title = Comprehensive Plan Update (2005) | publisher = City of Lock Haven | url =http://lockhavenpa.gov/wp-content/uploads/2015/01/2005_comp_plan.pdf |archive-url=https://web.archive.org/web/20150420184323/http://lockhavenpa.gov/wp-content/uploads/2015/01/2005_comp_plan.pdf|url-status=live|archive-date=April 20, 2015| access-date = September 21, 2007}}</ref> As the company grew, the original factory expanded to include engineering and office buildings. Piper remained in the city until 1984, when its new owner, [[EG&G#Lear Siegler Services, Inc.|Lear-Siegler]], moved production to [[Vero Beach, Florida]]. The Clinton County Historical Society opened the Piper Aviation Museum at the site of the former factory in 1985, and 10&nbsp;years later the museum became an independent organization.<ref name="plan"/>

The state of Pennsylvania acquired Central State Normal School in 1915 and renamed it Lock Haven State Teachers College in 1927. Between 1942 and 1970, the student population grew from 146 to more than 2,300; the number of teaching faculty rose from 25 to 170, and the college carried out a large building program. The school's name was changed to Lock Haven State College in 1960, and its emphasis shifted to include the humanities, fine arts, mathematics, and social sciences, as well as teacher education. Becoming Lock Haven University of Pennsylvania in 1983, it opened a branch campus in [[Clearfield, Pennsylvania|Clearfield]], {{convert|48|mi|km|0}} west of Lock Haven, in 1989.<ref name=lhuphistory/>

An {{convert|8|acre|ha|adj=on}} industrial area in Castanea Township adjacent to Lock Haven was placed on the National Priorities List of uncontrolled hazardous waste sites, commonly referred to as [[Superfund]] sites, in 1982. Drake Chemical, which went bankrupt in 1981, made ingredients for pesticides and other compounds at the site from the 1960s to 1981. Starting in 1982, the [[United States Environmental Protection Agency]] began a clean-up of contaminated containers, buildings, and soils at the site and by the late 1990s had replaced the soils. Equipment to treat contaminated groundwater at the site was installed in 2000 and continues to operate.<ref>{{cite web | title = Mid-Atlantic Superfund: Drake Chemical: Current Site Information | publisher = U.S. Environmental Protection Agency | url = http://www.epa.gov/reg3hwmd/npl/PAD003058047.htm | access-date = October 18, 2007|archive-url=https://web.archive.org/web/20150514224655/http://www.epa.gov/reg3hwmd/npl/PAD003058047.htm|archive-date=May 14, 2015|url-status=live}}</ref>