The story of the military unit organized by future U.S. President Teddy Roosevelt and its adventures in Cuba during the Spanish-American War of 1898.

In 1898, following the destruction of the Maine in Cuba, war is declared against Spain by the United States; and Theodore Roosevelt, Assistant Secretary of the Navy, along with Leonard Wood of the Army Medical Corps, are offered the eagles in the first volunteer regiments; but they decline and together assemble the Rough Riders, a motley assortment of volunteers, on the Exposition Grounds at San Antonio. Amidst the regiment are Happy Joe, who skips jail to enlist; his pursuer, a sheriff known as Hell's Bells; Bert Henley, a local boy; Van, a handsome New Yorker; and Dolly, who is the object of Bert's and Van's affections. When the regiment sees action in Cuba, the boys' intense rivalry turns into friendship; and when Bert is wounded, Van carries him back to base in San Juan, where he dies a hero. At the end of the war, Van carries the news to Dolly; later, with the inauguration of Roosevelt as President, Van and Dolly come to the reception with their two children.