Hancock is the most northern and the smallest of West Virginia's counties. It encompasses only 88.2 square miles. The Ohio River marks Hancock's northern and western borders with the state of Ohio. Pennsylvania is to the east and Brooke County to the south. Elevations in Hancock County range from 666 feet to 1,337 feet. The Ohio serves as an important transportation artery. CSX is the major railroad line. U.S. 22 bisects the southern end of the county on an east-west axis and is the major roadway. U.S. 30, the old Lincoln Highway and the first transcontinental road for motor vehicles, crosses the northern tip of the county. The principal state road, State Route 2, parallels the Ohio River, connecting Hancock County to Wheeling and points south.

Hancock County's population was an estimated 30,305 in 2012, making it one of the state's most densely populated counties. Hancock ranks high in per capita income and the educational level of its citizens.

Weirton, with an estimated 19,746 people in 2010, is the largest city. Weirton is situated in the extreme southern part of the county, with a small portion of the city in neighboring Brooke County. Founded in 1909 by Weirton Steel, it became the nation's largest unincorporated city, a distinction it retained until 1947 when voters approved a city charter. Weirton is the only American city whose boundaries touch two other state borders, Pennsylvania on the east and Ohio on the west.

Chester, with 2,585 people in 2010, is the second most populous town in Hancock County. Incorporated in 1907, Chester is located at the northern tip of the county. The county seat, New Cumberland, with a 2010 population of 1,103, received its charter from the state of Virginia in 1849. Hancock County has two sizable unincorporated communities, Newell and New Manchester. Newell is the home of the Homer Laughlin China Company, one of the county's largest employers. Tomlinson Run State Park is in Hancock County.

Hancock County has lost population since 1980. This trend reflects declining employment opportunities, particularly in industry. Earlier in the 20th century, the opposite was true. As manufacturing jobs proliferated, people moved to Hancock County, and the population grew at a steady, sometimes spectacular, rate. The county population peaked in 1980 at 40,418. Weirton, whose highest population was 28,201 in 1960, had lost nearly 30 percent of that total by 2010.

In the 18th century ownership of the upper Ohio Valley was contested among the European colonial powers of Great Britain and France, the colonies of Virginia and Pennsylvania, and the Indians of the surrounding region. The British eradicated French claims in the French and Indian War, which ended in 1763, but brutal fighting with the Indians continued into the 1790s. In the midst of this period, the first documented permanent settlements in what is today Hancock County were established. Harmon Greathouse arrived in 1771, and in 1776 John Holliday was operating a trading post at Hollidays Cove. The Virginia General Assembly created Brooke County from northern Ohio County in 1797; and on January 15, 1848, under the leadership of Joseph Bambrick, an Irish immigrant and member of the Virginia legislature, the northern half of Brooke became Hancock County. The county was named for John Hancock.

Though Virginia was a slave state, slavery scarcely existed in Hancock County. The 1850 census listed three slaves, and in 1860 there were only two slaves in a county population of 4,445. Hancock voters overwhelmingly rejected the Virginia secession ordinance of 1861 (23—743) and later supported the creation of West Virginia by a tally of 263—67. More than 400 residents served in the Union army during the Civil War.

The county economy in the late 19th century remained very largely agricultural, with some transportation improvements and a few manufacturing and mining establishments. The first railroad received its charter in 1860. Abundant clay deposits led to the formation of firms producing bricks and pottery. An early natural gas well was drilled in 1862, and by 1864 natural gas was used to produce carbon black for printing ink. Intensive industrial development did not begin until the early 20th century, when two new enterprises transformed the county's economic base.

The Homer Laughlin China Company of East Liverpool, Ohio, purchased the Newell farm in 1902 across the Ohio River in Hancock County. At Newell, the company built the world's largest pottery, manufacturing dishes for household, hotel, and restaurant use. It began production of its popular "Fiesta" tableware in the 1930s. In 1909, Ernest T. Weir established Weirton Steel and the town of Weirton about one mile north of Hollidays Cove. Coincidentally, one of the first iron furnaces west of the Allegheny Mountains, the Peter Tarr Furnace, had operated in proximity to the site of the new mills from the 1790s until at least the second decade of the 19th century. Tarr produced iron cannonballs for Commodore Oliver Perry's successful campaign against the British on Lake Erie during the War of 1812.

By the 1950s, Weirton Steel had become the state's largest employer and taxpayer, generating jobs for more than 13,000 and sending tens of millions in tax revenue to the state capital of Charleston. In 1984, Weirton Steel became the nation's largest employee-owned company with the establishment of an Employee Stock Ownership Plan. In 2004, International Steel Group purchased Weirton Steel, marking the end of worker ownership at the company. In 2005, International Steel Group merged with Mittal Steel and then with Arcelor. The Weirton plant is part of the ArcelorMittal global conglomerate.

Recreational tourism is Hancock County's growth industry in the early 21st century. Mountaineer Casino Racetrack & Resort is a major employer in the county.