The city of Lock Haven is the county seat of Clinton County, in the U.S. state of Pennsylvania. Located near the confluence of the West Branch Susquehanna River and Bald Eagle Creek, it is the principal city of the Lock Haven, Pennsylvania, micropolitan statistical area, itself part of the Williamsport–Lock Haven combined statistical area. At the 2010 census, Lock Haven's population was 9,772.

Built on a site long favored by pre-European peoples, Lock Haven began in 1833 as a timber town and a haven for loggers, boatmen, and other travelers on the river or the West Branch Canal. Resource extraction and efficient transportation financed much of the city's growth through the end of the 19th century. In the 20th century, a light-aircraft factory, a college, and a paper mill, along with many smaller enterprises, drove the economy. Frequent floods, especially in 1972, damaged local industry and led to a high rate of unemployment in the 1980s.

The city has three sites on the National Register of Historic Places—Memorial Park Site, a significant pre-European archaeological find; Heisey House, a Victorian-era museum; and Water Street District, an area with a mix of 19th- and 20th-century architecture. A levee, completed in 1995, protects the city from further flooding. While industry remains important to the city, about a third of Lock Haven's workforce is employed in education, health care, or social services.

In the early 18th century, a tribal confederacy known as the Six Nations of the Iroquois, headquartered in New York, ruled the Indian (Native American) tribes of Pennsylvania, including those who lived near what would become Lock Haven. Indian settlements in the area included three Munsee villages on the 325-acre Great Island in the West Branch Susquehanna River at the mouth of Bald Eagle Creek. Four Indian trails, the Great Island Path, the Great Shamokin Path, the Bald Eagle Creek Path, and the Sinnemahoning Path, crossed the island, and a fifth, Logan's Path, met Bald Eagle Creek Path a few miles upstream near the mouth of Fishing Creek. During the French and Indian War (1754–63), colonial militiamen on the Kittanning Expedition destroyed Munsee property on the Great Island and along the West Branch. By 1763, the Munsee had abandoned their island villages and other villages in the area.

With the signing of the first Treaty of Fort Stanwix in 1768, the British gained control from the Iroquois of lands south of the West Branch. However, white settlers continued to appropriate land, including tracts in and near the future site of Lock Haven, not covered by the treaty. In 1769, Cleary Campbell, the first white settler in the area, built a log cabin near the present site of Lock Haven University of Pennsylvania, and by 1773 William Reed, another settler, had built a cabin surrounded by a stockade and called it Reed's Fort. It was the westernmost of 11 mostly primitive forts along the West Branch; Fort Augusta, at what is now Sunbury, was the easternmost and most defensible. In response to settler incursions, and encouraged by the British during the American Revolution (1775–83), Indians attacked colonists and their settlements along the West Branch. Fort Reed and the other white settlements in the area were temporarily abandoned in 1778 during a general evacuation known as the Big Runaway. Hundreds of people fled along the river to Fort Augusta, about 50 miles from Fort Reed; some did not return for five years. In 1784, the second Treaty of Fort Stanwix, between the Iroquois and the United States, transferred most of the remaining Indian territory in Pennsylvania, including what would become Lock Haven, to the state. The U.S. acquired the last remaining tract, the Erie Triangle, through a separate treaty and sold it to Pennsylvania in 1792.

Lock Haven was laid out as a town in 1833, and it became the county seat in 1839, when the county was created out of parts of Lycoming and Centre counties. Incorporated as a borough in 1840 and as a city in 1870, Lock Haven prospered in the 19th century largely because of timber and transportation. The forests of Clinton County and counties upriver held a huge supply of white pine and hemlock as well as oak, ash, maple, poplar, cherry, beech, and magnolia. The wood was used locally for such things as frame houses, shingles, canal boats, and wooden bridges, and whole logs were floated to Chesapeake Bay and on to Baltimore, to make spars for ships. Log driving and log rafting, competing forms of transporting logs to sawmills, began along the West Branch around 1800. By 1830, slightly before the founding of the town, the lumber industry was well established.

The West Branch Canal, which opened in 1834, ran 73 miles from Northumberland to Farrandsville, about 5 miles upstream from Lock Haven. A state-funded extension called the Bald Eagle Cut ran from the West Branch through Lock Haven and Flemington to Bald Eagle Creek. A privately-funded extension, the Bald Eagle and Spring Creek Navigation, eventually reached Bellefonte, 24 miles upstream. Lock Haven's founder, Jeremiah Church, and his brother, Willard, chose the town site in 1833 partly because of the river, the creek, and the canal. Church named the town Lock Haven because it had a canal lock and because it was a haven for loggers, boatmen, and other travelers. Over the next quarter century, canal boats 12 feet wide and 80 feet long carried passengers and mail as well as cargo such as coal, ashes for lye and soap, firewood, food, furniture, dry goods, and clothing. A rapid increase in Lock Haven's population (to 830 by 1850) followed the opening of the canal.

A Lock Haven log boom, smaller than but otherwise similar to the Susquehanna Boom at Williamsport, was constructed in 1849. Large cribs of timbers weighted with tons of stone were arranged in the pool behind the Dunnstown Dam, named for a settlement on the shore opposite Lock Haven. The piers, about 150 feet from one another, stretched in a line from the dam to a point 3 miles upriver. Connected by timbers shackled together with iron yokes and rings, the piers anchored an enclosure into which the river current forced floating logs. Workers called boom rats sorted the captured logs, branded like cattle, for delivery to sawmills and other owners. Lock Haven became the lumber center of Clinton County and the site of many businesses related to forest products.

The Sunbury and Erie Railroad, renamed the Philadelphia and Erie Railroad in 1861, reached Lock Haven in 1859, and with it came a building boom. Hoping that the area's coal, iron ore, white pine, and high-quality clay would produce significant future wealth, railroad investors led by Christopher and John Fallon financed a line to Lock Haven. On the strength of the railroad's potential value to the city, local residents had invested heavily in housing, building large homes between 1854 and 1856. Although the Fallons' coal and iron ventures failed, Gothic Revival, Greek Revival, and Italianate mansions and commercial buildings such as the Fallon House, a large hotel, remained, and the railroad provided a new mode of transport for the ongoing timber era. A second rail line, the Bald Eagle Valley Railroad, originally organized as the Tyrone and Lock Haven Railroad and completed in the 1860s, linked Lock Haven to Tyrone, 56 miles to the southwest. The two rail lines soon became part of the network controlled by the Pennsylvania Railroad.

During the era of log floating, logjams sometimes occurred when logs struck an obstacle. Log rafts floating down the West Branch had to pass through chutes in canal dams. The rafts were commonly 28 feet wide—narrow enough to pass through the chutes—and 150 feet to 200 feet long. In 1874, a large raft got wedged in the chute of the Dunnstown Dam and caused a jam that blocked the channel from bank to bank with a pile of logs 16 feet high. The jam eventually trapped another 200 log rafts, and 2 canal boats, The Mammoth of Newport and The Sarah Dunbar.

In terms of board feet, the peak of the lumber era in Pennsylvania arrived in about 1885, when 1.9 million logs went through the boom at Williamsport. These logs produced a total of about 226 million board feet of sawed lumber. After that, production steadily declined throughout the state. Lock Haven's timber business was also affected by flooding, which badly damaged the canals and destroyed the log boom in 1889.

The Central State Normal School, established to train teachers for central Pennsylvania, held its first classes in 1877 at a site overlooking the West Branch Susquehanna River. The small school, with enrollments below 150 until the 1940s, eventually became Lock Haven University of Pennsylvania. In the early 1880s, the New York and Pennsylvania Paper Mill in Castanea Township near Flemington began paper production on the site of a former sawmill; the paper mill remained a large employer until the end of the 20th century.

As older forms of transportation such as the canal boat disappeared, new forms arose. One of these, the 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, about 3 miles 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, 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, 3 miles south of Mill Hall, and to Avis 10 miles 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.

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. 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, 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 years later the museum became an independent organization.

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, 48 miles west of Lock Haven, in 1989.

An 8-acre 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.