Clarksburg, in north-central West Virginia, is the county seat of Harrison County and one of the state's oldest cities. Clarksburg is located at the junction of U.S. 50 and U.S. 19, two miles west of the junction of U.S. 50 with Interstate 79. The city lies at an elevation of 1,007 feet at the junction of Elk Creek and the West Fork of the Monongahela River. The population in 2020 was 16,039, a number that has remained relatively steady during the 21st century.

Two miles south of town on U.S. 19 are two prehistoric burial mounds. The first European to claim land in the area was a trapper named John Simpson, in 1764. The first permanent settler was Daniel Davisson, who about 1773 acquired 400 acres of land where Clarksburg is now located. Clarksburg became the county seat when Harrison County was formed in 1784. Named for the Revolutionary War hero, George Rogers Clark, the town was chartered in 1785.

Clarksburg's early economy centered around such small industries as a gristmill, a tannery, pottery, and saltworks, as well as the county government. Construction of the first courthouse began in 1787. That building was followed by four increasingly larger courthouses, the most recent one completed in 1932.

In 1787, the Virginia General Assembly established the Randolph Academy at Clarksburg, the first such educational institution west of the Alleghenies. In 1819, Clarksburg was chosen as the site of the first federal court west of the Alleghenies. The new court's first judge was John George Jackson, uncle of Confederate Gen. Thomas J. "Stonewall" Jackson.

Poor transportation slowed development until the 1830s, when the Northwestern Turnpike was built from Winchester to Parkersburg via Romney and Clarksburg. The arrival of the Baltimore & Ohio (B&O) Railroad in the mid-1850s opened the county to development. During the Civil War, the B&O line made Clarksburg an important Union supply base.

Clarksburg was the site of an important 1841 convention demanding free schools in Virginia and an 1861 rally that helped start the West Virginia statehood movement.

The availability of natural resources, coupled with easy access to railroad facilities, attracted industry and manufacturing to Clarksburg, including chemical plants, brickworks, potteries, foundries and machine shops, hardwood and casket companies, glass factories (including the Akro-Agate marble company), and the Jackson (later Phillips) Sheet and Tin Plate Company, the forerunner of Weirton Steel. Economic development brought successive waves of immigrants in the 19th and early 20th centuries, including Irish, Italians, Greeks, French, Belgians, and Spanish.

In 1887, the city laid its first six miles of water lines; downtown streets were lit by electricity in 1889. Telephone service, among the first in the state, was in place by 1891. In 1900, the first sewer lines were installed, Main and Pike streets were paved with brick, and the city's first trolley tracks were laid. Early 20th century Clarksburg boasted eight banks, three hospitals, and several fine hotels, including the elegant seven-story Waldo, which opened in 1909. The seven-story Empire Bank building went up in 1907, the nine-story Goff Building in 1911, and the 10-story Union Bank in 1912.

By 1929, Clarksburg had reached its peak population of 35,115. During the Depression the city lost industry and population, but during World War II the railroad again made it a central clearinghouse. New development came with the construction in the 1970s of Interstate 79 and the new four-lane U.S. 50 Appalachian Corridor D connecting I-79 to I-77, but plant closings in the 1980s had a negative impact. New expansion in the government and technology sectors began in the 1990s, including the relocation of the FBI Criminal Justice Information Services Center to Clarksburg and construction of a new federal building and a new building to house Fairmont State University's Clarksburg branch.

The city has a daily newspaper, three local television stations, and six radio stations. Air transportation is provided by nearby North Central West Virginia Airport at Bridgeport. The West Virginia Italian Heritage Festival, held each Labor Day weekend, has drawn thousands of visitors to Clarksburg each year since 1979.

Clarksburg was the birthplace of a number of prominent West Virginians, among them Confederate generals Stonewall Jackson and William “Mudwall” Jackson; John W. Davis, U.S. solicitor general, ambassador to Great Britain, and Democratic nominee for president in 1924; Cyrus Vance, secretary of state under President Jimmy Carter; filmmaker Pare Lorentz; and author Meredith Sue Willis. It was the longtime home of early statehood leader John S. Carlile; the state's 17th governor, Howard M. Gore; and Louis Johnson, assistant secretary of war under President Franklin D. Roosevelt and President Harry Truman's secretary of defense. Clarksburg is the burial site of Mary Payne Jackson and Mary Coles Payne, respectively the sister and mother of Dolley Payne Madison, wife of President James Madison.

It was home to notorious murderer Harry Powers, who inspired author Davis Grubb’s novel The Night of the Hunter. Clarksburg also was the childhood home of author Agnes Smith,