William Rufus Day (April 17, 1849 – July 9, 1923) was an American diplomat and jurist who served as an associate justice of the Supreme Court of the United States from 1903 to 1922.

[3] For twenty-five years, Day worked as a criminal defense and corporate lawyer in the growing industrial town while participating in Republican politics.

[1] Five months later, Day vacated his cabinet position to helm the United States Peace Commission formed to negotiate an end to the Spanish–American War with Spain.

[4] His final diplomatic effort was to lead the United States Peace Commission to Paris and sign the treaty ending the war.

[6] The United States Senate confirmed the nomination on February 23, 1903,[5] and Day took the judicial oath of office on March 2, 1903.

[6] Day delivered the opinion of the Court in Weeks v. United States, where the highest Court ruled that the warrantless seizure of documents from a private home violated the Fourth Amendment prohibition against unreasonable searches and seizures, and evidence obtained in this manner is excluded from use in federal criminal prosecutions.

Harding considered the proposal but Taft felt, when he learned of this plan, that a short-term appointment would not serve the office well, and that once confirmed by the Senate, the memory of Day would grow dim.

[8] He would often leave the Court after oral argument and go straight to Boundary Field to watch the Washington Senators play.