Miles Poindexter, attorney, member of Congress from Washington State, and diplomat, was born in 1868 in Tennessee and grew up in Virginia. He attended Washington and Lee University (undergraduate and law school), receiving his law degree in 1891. He moved to Walla Walla, Washington, was admitted to the bar and began his law practice. He entered politics soon after his arrival and ran successfully for County Prosecutor as a Democrat in 1892. Poindexter moved to Spokane in 1897 where he continued the practice of law. He switched to the Republican Party in Spokane, where he received an appointment as deputy prosecuting attorney (1898-1904). In 1904 he was elected Superior Court Judge.

Poindexter became identified with progressive causes and it was as a progressive Republican and a supporter of Theodore Roosevelt that he was elected to the House of Representatives in 1908 and to the Senate in 1910. He was an outspoken member of the progressive Republican bloc, known as "insurgents," who revolted against the leadership of Congress between 1909 and 1912. After Roosevelt's split from the Republican Party during the 1912 presidential campaign, Poindexter reluctantly joined the Progressive Party. Dissatisfaction with Wilson's foreign policy and his own loss of enthusiasm for reform measures coincided with his return to the Republican Party in 1915. His efforts on behalf of tariff reform and the regulation of the railroads, banks and other "interests" pleased his political supporters in Washington State, and he won another term to the Senate in 1916.

During his tenure as Senator, Poindexter served on the Interstate Commerce, Judiciary, Mines and Mining, Naval Affairs, Post Office and Post Roads, Pacific Islands and Puerto Rico, and Indian Depredations committees, as well as Committees on Expenditures in the Interior Department and the War Department. One of Poindexter's more notable legislative proposals dealt with the problem of unemployment in a manner that foreshadowed the New Deal. In 1913 he introduced a bill which would have created an "industrial army" to construct public works. He was also a proponent of military preparedness and favored expansion of the Navy.

Poindexter was intensely nationalistic and worked to suppress opposition to America's entry into World War I. He favored wartime censorship, the Sedition Act, and considered pacifism disloyal. He also spoke strongly against "alien slackers," immigrants who turned in their first citizenship papers to avoid the draft. After the war he was an outspoken critic of President Wilson and the League of Nations. He believed Wilson was sympathetic to Bolshevism and criticized the administration for leniency in handling the prosecution of radicals. His position against labor unions and radical groups contributed to the "Red Scare" of 1919-1920.

Poindexter received national recognition, in particular, for his stand against the League of Nations and being pro-American and anti-anarchists/Bolsheviks. This national recognition was one factor in his decision to run for the Republican presidential nomination in 1920. He was the first Republican to declare his candidacy (October 26, 1919) but lost the nomination to Warren G. Harding.

After the 1920 election Poindexter became a Harding Republican, favoring business interests over those of labor and farmers. In 1922, he lost his Senate re-election bid to C.C. Dill, a progressive Democrat. In 1923 President Harding appointed Poindexter ambassador to Peru, where he served until 1928. He made another unsuccessful attempt to regain his Senate seat that year. After the death of his wife in 1929 he returned to Virginia. Following his retirement from political life, Poindexter produced three manuscripts about the Inca civilization, two of which ( and ) were published. He died in Virginia in 1946.