Lawyers historically preferred longer pieces of paper when taking notes and recording official documents, hence the name legal paper. Legal sized paper is 8.5 inches by 14 inches long.
The Committee on the Simplification of Paper Sizes, a branch of the U.S. Bureau of Standards, began standardizing paper size in the early 1920s. The result was two official paper sizes in the United States: legal and letter. Standard letter sized paper is 8.5 by 11 inches.
The legal pad received its name for its popularity in the law field. Paper mill worker Thomas Holley began making and selling inexpensive paper pads using scraps of discarded paper. A judge in Holyoke, Massachusetts, was the first to start using one of Holley's pads in a court room, eventually leading to similar paper pads being called legal pads.