The notable document rejected at the Senate in 1919, leading to U.S. non-participation in the League of Nations, was the Treaty of Versailles. After World War I, the treaty outlined the terms for peace and included the Covenant of the League of Nations, an international organization aimed at preventing future conflicts. Despite President Woodrow Wilson's advocacy for the league as a means to ensure global stability, the Senate, primarily due to concerns over entangling alliances and national sovereignty, ultimately voted against ratification. This rejection had significant implications, as the U.S. absence weakened the League's authority and effectiveness, contributing to the instability that preceded World War II.