Theodore Frelinghuysen Singiser (March 15, 1845 – January 23, 1907) was a Delegate from Idaho Territory. Born in Churchtown in Cumberland County, Pennsylvania, Singiser attended the common schools. He learned the art of printing, and then enlisted in the Union Army as a private in Company E, Sixth Regiment, Pennsylvania Reserves, on June 6, 1861. He served as assistant assessor of internal revenue in 1866 and 1867, and engaged in mercantile and editorial pursuits. He studied law, and was admitted to the bar in Washington, D.C., in 1878. Singiser was employed in the United States Treasury from June 1, 1875, to May 31, 1879. He was appointed receiver of public moneys at Oxford, Idaho, in February 1879. He engaged in mining in Idaho and Utah, and was Secretary of the Territory of Idaho in 188