Watson C. Squire (May 18, 1838 - June 7, 1926) was a United States Senator from Washington. Born in Cape Vincent, New York, he attended the public schools, Falley Seminary (in Fulton, New York) and Fairfield Seminary (Herkimer County, New York). He graduated from Wesleyan University in 1859 and was principal of the Moravia Institute. During the Civil War, he enlisted in Company F, Nineteenth Regiment, New York Volunteer Infantry, in 1861; he was promoted to the rank of first lieutenant, and was mustered out the same year. He graduated from the Cleveland Law School in 1862 and was admitted to the bar the same year, commencing practice in Cleveland, Ohio. He raised a company of sharpshooters, of which he was commissioned captain. He was made judge advocate of the district of Tennessee, with headquarters in Nashville; in 1865, he was discharged with the rank of captain and was subsequently brevetted major, lieutenant colonel, and colonel. Subsequently, Squire was employed with the Remington Arms Company and purchased large holdings in the Territory of Washington in 1876.
Squire moved to Seattle in 1879, and was Governor of the Territory of Washington from 1884 to 1887. Upon the admission of Washington as a State into the Union in 1889, Squire was elected as a Republican to the U.S. Senate; he was reelected in 1891, and served from November 20, 1889, to March 3, 1897. He was an unsuccessful candidate for reelection in 1897. While in the Senate, he was chairman of the Committee on Coast Defenses (Fifty-second and Fifty-fourth Congresses) and a member of the Committee on Transportation Routes to the Seaboard (Fifty-second Congress). He retired from the practice of law and devoted his time to management of his properties in Seattle; he was organizer and president of the Union Trust Co. and the Squire Investment Co. He died in Seattle; interment was in Washelli Cemetery.