Westmoreland Davis was born at sea, 21 August 1859, to Annie Morriss (ca. 1835-25 Jan 1921) and Thomas Gordon Davis (1828-1860). Thomas Davis managed five plantations in Mississippi, including two inherited by his wife, and spent much of his time traveling. Annie Davis spent most of her time at his family home in Stateburg, SC. Shortly after Westmoreland Davis' birth, his father, brother and sister died in quick succession. He and his mother moved to Richmond, VA to live with her uncle Richard Morriss (ca. 1822-1867). After the end of the Civil War the Davis's were reduced to penury by the mismanagement of their plantations and legal obstacles to monies from bonds purchased by her father, Christopher Staats Morriss (1797-1850).

Davis entered Virginia Military Institute as a scholarship student in 1873 at the age of 14. After graduating in 1877, Davis worked for the Richmond & Allegheny railroad until 1883, when he entered University of Virginia for a year's study in order to prepare for law school. He attended Columbia University Law School in New York City, graduating in 1886.

By the 1890's Davis was a successful corporate lawyer. He married Marguerite Inman (1 Aug 1882-13 Jul 1963) in 1892. The couple lived in Manhattan for a year before moving to Orange County, NY, where they resided for nine years. The Davis's enjoyed fox hunting and were members of the Orange County Hunt Club.

In 1903 they purchased Morven Park in Loudoun County, VA. Davis resigned from his legal practice and the couple moved to Virginia permanently. They joined the Loudoun Hunt Club, and entertained frequently. Davis concentrated his attention on improving the farm and became interested in livestock breeding and an advocate for progressive farm techniques. In 1909 he was elected president of the Virginia State Farmers' Institute, an association of farmers who promoted education. Under his leadership, the Institute developed into an effective lobbying organization.

Davis decided in 1915 to enter the 1917 Democratic gubernatorial primary. He did not expect to win; rather, he hoped the run would put him in a position to win in 1921. Running as an independent Democrat, he faced one other independent candidate in addition to the man backed by the organization that controlled the Democratic party. The machine had settled on Prohibition as a campaign focal point, and Davis' rivals ran as "drys." Davis was known to be an opponent of Prohibition, although he tried to downplay his position and took care to say that he would support any laws on the books if he were elected. He chose to focus his campaign on areas such as agriculture, education and establishing an executive budget. In spite of continuous attacks by the Prohibitionists, Davis won the primary easily in August 1917.

The Republicans seized on the Prohibition theme, hoping to lure "dry" Democrats to their side. However, in general neither side was able to generate much interest as the war dominated the news. Davis won by a generous margin in the general election. During his term of office, Davis' efforts to make changes to institute a more businesslike approach to government faced opposition from the machine-dominated General Assembly. In spite of efforts to thwart him, Davis was able to institute some progressive changes.

Davis ran for re-election in 1922 but was resoundingly defeated. During his administration the machine lost its leader, Senator Thomas Martin, and appeared to weakening. However, by 1922 the party organization was energized with the emergence of Harry Flood Byrd (10 Jun 1887-20 Oct 1966), who was a sharp Davis critic, as its leader. Davis lost the race to Claude Swanson (1862-1939).

In the years following his defeat, Davis focused his attention on opposition to the Byrd Organization and its dominance of the Virginia political system, largely through editorial comment in the journal Southern Planter, which he purchased in 1912. He re-entered the political scene for the 1932 election. Davis campaigned vigorously for Franklin Delano Roosevelt (30 Jun 1882-12 Apr 1945), contributing money and traveling to make speeches in support of him. He was also an avid supporter and promoter of the New Deal. Davis died 2 September 1942 at Morven Park.