Henry Gassaway Davis was born near Woodstock, Howard County, Maryland, the son of Louisa Warfield (née Brown; March 10, 1799 – July 23, 1868) and merchant Caleb Dorsey Davis (March 3, 1792 – September 4, 1850). He was the great-great-great-grandson of Maryland pioneer Thomas Davis, and the great-great-great-great-grandson of Maryland politician and justice Colonel Nicholas Gassaway, both of whom were of Welsh ancestry and emigrated to Maryland in the mid 17th century. Stage coaches stopped at Woodstock five days a week en route to Washington, D.C., and Davis later often recalled one of his earliest memories–witnessing the groundbreaking of the county’s first railroad in Baltimore from atop his father’s shoulders on July 4, 1828. He had three brothers and a sister. His father’s business prospered until he won a contract to grade a section of road between Baltimore and Frederick, Maryland, which caused heavy losses. Creditors caused even the family’s horses and carriages to be sold, which proved devastating to Caleb Davis’s health.

On February 22, 1853, in Frederick County, Maryland. Davis married Katherine Ann Salome Bantz. Henry and Katherine had eight children, three of whom died in infancy. Seven of their eight children have been identified, as follows:

When his family’s finances collapsed, Davis (then 15 years old) abandoned his education and took a job carrying water for workmen at a nearby quarry, then became caretaker of “Waverly” a nearby farm own by Governor Howard. When Davis was 20, the B&O completed track from Frederick to Cumberland, and needed men to run the trains and handle cargo. Thus Davis went to work for the Baltimore and Ohio Railroad as a brakeman. His hard work and enthusiasm drew the attention of the railroad’s president, Thomas Swann, who promoted him to freight conductor, then passenger conductor. Davis met many statesmen, including Senators Henry Clay of Kentucky (whom Davis came to admire and received invitations to visit at his home in Ashland, Kentucky), Thomas H. Benton of Missouri, Lewis Cass of Michigan, Benjamin Wade and Thomas Corwin of Ohio, and Stephen A. Douglas of Illinois — all of whom embarked the B&O train in Cumberland to reach Washington, D.C. (or disembarked on the reverse route). Davis also often stayed at a hotel in Washington between trips, and conversed with other notables, including Senators William C. Rives of Virginia, John C. Calhoun of South Carolina and Daniel Webster of Massachusetts. When the B&O finally completed track to Wheeling on the navigable Ohio River, Davis was put in charge of the Piedmont station. It was a crucial station because it was at the foot of a mountain, where trains traveling eastward added engines to surmount the slope. Until the railroad completed a house for him (so his new wife could join him), Davis lived in a box car, and also came to admire the natural landscape of the Allegheny Mountains. After four years, his brother Thomas joined him, and they established a store, often trading farm products for manufactured goods such as jeans, shoes, calico and sugar. In 1858, Davis resigned his railroad job to concentrate on the firm, Henry G. Davis & Company.

When the Civil War began, even the B & O’s President, John Work Garrett initially sympathized with the Southern cause. However, the B&O was crucial for the Union armies. Davis favored Union and also admired the new President Abraham Lincoln. When Confederate raiders attacked the B&O and destroyed track and bridges, part of Davis’ job was to restore service and keep the supplies moving. Many in western Virginia likewise favored the Union, and met in two Wheeling Conventions, then adopted a statehood referendum and constitution, eventually becoming the 35th state. In 1865, Davis would be elected to the West Virginia House of Delegates as one of Hampshire County’s representatives.

In 1865 Davis was elected a member of the West Virginia House of Delegates. The following year, he founded the Potomac and Piedmont Coal and Railway Company with the intent of furnishing transportation to his coal mining and timbering interests. The company was given the right to construct railroad grades in Mineral, Grant, Tucker and Randolph counties. He became a state senator in 1869. In 1870, he was elected to the United States Senate, serving two terms, with his service ending in 1883.

In 1904, Davis became the Democratic nominee for vice president on a ticket with Alton B. Parker. Parker and Davis lost to the Republican ticket of Theodore Roosevelt and Charles Fairbanks by a wide margin. At the age of 80, Davis was and remains the oldest person to be nominated for president or vice president on a major party ticket. He was chosen primarily because of his ability to provide much needed funds to the campaign.

Davis in his last years acted as chairman of the permanent Pan American Railway Committee (1901–1916) and also donated land to build Davis and Elkins College in Elkins, West Virginia. He died in Washington, D.C. on March 11, 1916 at the age of 92. He was interred in the Maplewood Cemetery in Elkins. A bronze equestrian statue of Davis was erected in 1927, at Sycamore Street and Randolph Avenue in Elkins, with an identical twin in Davis Park in downtown Charleston, West Virginia.