John Jacob Cornwell (July 11, 1867 - September 8, 1953) was the 15th governor of West Virginia, serving from 1917 to 1921 and leading the state during World War I. Born on a farm in the community of Mole Hill (later Mountain) in Ritchie County, Cornwell as a child moved with his family to Hampshire County. He was educated in Hampshire County public schools, at Shepherd College (now Shepherd University), and at West Virginia University, which he attended in 1889-90. Formerly a teacher at Romney, he read for the law there, became president of the local bank, invested in railroads and apple orchards, and edited the Hampshire Review, a newspaper that he purchased with his brother in 1890. After passing the bar examination in 1894, he handled cases for the Baltimore & Ohio Railroad (B&O), beginning a lifelong relationship with the corporation.

A conservative Democrat, Cornwell was a state senator from 1899 to 1905 and the Democratic nominee for governor in 1904, losing to William M. O. Dawson. He was elected governor in 1916, defeating progressive Republican Ira Robinson, a state supreme court justice, by less than 3,000 votes. Cornwell took the oath as governor only 33 days before the United States declared war against Germany, the beginning of American involvement in World War I. He called the state legislature into emergency session, aware of the critical role West Virginia would play in supplying industrial and agricultural resources for the war mobilization. The lawmakers approved Cornwell's plan for a West Virginia Council of Defense, an ad hoc body with extensive powers to regulate wartime production. He supported and got a compulsory work law requiring all able-bodied males (there were some exemptions) 16 to 60 to work at least 36 hours weekly for the duration of the war.

To foster wartime unity, Cornwell sought to paper over his party's poor relationship with Black West Virginians even as he assaulted their power base. He held no political loyalties to West Virginia's African-American voters, and his Republican opponent had swept most Black precincts. Blacks had capitalized on their political enfranchisement in West Virginia to resist systematic bigotry, using their political leverage to considerable effect under Republican administrations dating back to 1897. Cornwell embarked on a silent purge of Black Republican appointees to the state's bureaucracy and cut state appropriations to Black institutions. To create the appearance of patriotic solidarity, however, he appointed prominent African-Americans to an advisory committee of the State Defense Council. Cornwell thrived in the wartime climate of emergency, using the state and local defense council network to urge West Virginians to maximize production and be on guard for possible disloyal neighbors.

With the Armistice, the governor turned much of his energy to suspected new threats to American security, emerging as a national spokesman against organized labor's attempts to extend wartime gains into the postwar era. Although Cornwell had courted and won the support of Socialist voters in 1916, by 1919 his rhetoric incorporated socialism, Bolshevism, and organized labor into one vast conspiracy. Cornwell's inflammatory pronouncements during national coal and steel strikes in 1919 and during the West Virginia Mine Wars of 1919-21 reflect some of the more divisive tactics of that volatile period. His fevered rhetoric against such relatively mild reform proposals as public oversight of railroads, combined with the transparently antilabor thrust of his promotion in 1919 of Red Flag legislation and Constabulary legislation (creating the State Police), militated against labor-management reconciliation in the troubled postwar Red Scare years. His presidency (while still in office as governor) of a statewide open-shop propaganda organization, the American Constitutional Association, punctuated Cornwell's increasing intolerance for alternatives to corporate rule in the state and nation.

Cornwell's position on organized labor did not stem from any denial that injustices in American industry needed mediation. He supported mine safety and child labor legislation, the eight-hour work day, and workers' compensation. But to Cornwell such advances should be bestowed by enlightened industrial leaders and not the product of collective militancy by workers' organizations. His logic dictated that industrial unions, which he interpreted as impediments to the natural growth of business, were unpatriotic. He therefore felt justified in carrying the fervent language of the wartime crusades into the arena of labor-management conflict. Convinced that attempts by the United Mine Workers of America (UMWA) to organize southern West Virginia miners represented incipient industrial revolution, Cornwell suspected that his highly visible stand against the union marked him for assassination by UMWA leaders.

No assassination attempt materialized, but the explosiveness of labor management conflict during Cornwell's term (including the bloody Matewan Massacre), following the ideological excesses of the wartime mobilization, loom large in Cornwell's legacy. They overshadow such accomplishments as a good roads amendment, the rationalization of the state budget process, and progress toward resolution of the Virginia debt controversy.

When he left the governor's office, Cornwell became a director and general counsel of the B&O and remained highly influential in the conservative wing of the West Virginia Democratic Party. He maintained residences in Baltimore and Romney, dying in Cumberland, Maryland, at the age of 86.