Davis was known especially for paintings of vertical stripes of color, and as a member of the group of abstract painters known as the Washington Color School.

Davis was born in Washington, D.C. and spent nearly all his life there. Before he began to paint in 1949, he worked as a sportswriter, covering the Washington Redskins and other local teams. In 1965, he participated in the Washington Color Painters exhibit at the Washington Gallery of Modern Art which traveled to four other venues around the US, including the University of Texas Art Galleries. This exhibition launched the recognition of the Washington Color School as a regional movement in which Davis was a central figure. Other key figures include Kenneth Noland, Morris Louis, Paul Reed, Thomas Downing and Howard Mehring.

Though Davis worked in a variety of media and styles, including ink, oil, acrylic, video, and collage, he is best known by far for his acrylic paintings of colorful vertical stripes, which he began to paint in 1958. The paintings, and his often-overlooked drawings, typically repeat particular colors to create a sense of rhythm and repetition with variations. One of his best-known paintings, Black Grey Beat (1964), owned by the Smithsonian American Art Museum reinforces musical comparisons in its title.

In 1972 Davis created Franklin's Footpath, which was at the time was considered one of the world's largest artworks, by painting colorful stripes on the street in front of the Philadelphia Museum of Art, and also in that year he created one of the world's largest paintings, Niagara (43,680 square feet), in a parking lot in Lewiston, NY.

Davis began teaching in 1966 at the Corcoran School of Art, where he became a permanent member of the faculty. Davis died in 1985. His works are in the collections of, among others, the Academy Art Museum, Easton, Maryland; Corcoran Gallery of Art, Washington D.C.; the Solomon R. Guggenheim Museum, New York; and The Phillips Collection, Washington D.C.