The Treaty of Versailles

… to end of World War I was signed on this date in 1919, five years to the day after the assassination that sparked the war.

The United States Senate never ratified the Treaty. Ratification required two-thirds approval of the Senate. Some Republican senators opposed the Treaty because a Democratic president had negotiated it; some Democratic senators opposed the Treaty because they had German-American or Irish (that is, anti-British) constituents.