Frank D. Baldwin, United States general, son of Francis L. and Betsy Ann (Richards) Baldwin, was born on June 26, 1842, near Manchester, Michigan. With two half-sisters he was reared and schooled in Constantine, Michigan, then briefly attended Hillsdale Baptist College in that state. On September 5, 1862, during the Civil War, Baldwin enlisted as a first lieutenant in the Nineteenth Michigan Infantry. He was captured at the battle of Thompson's Station, Tennessee (March 4–5, 1863), confined briefly at Libby Prison in Richmond, and then exchanged. In March 1864 Baldwin, now a captain, joined William T. Sherman's campaign against Atlanta and the March to the Sea. He earned a Medal of Honor at the battle of Peachtree Creek, Georgia, on July 20, 1864. He entered the postwar regular army as a second lieutenant early in 1866, was promoted to first lieutenant in the Nineteenth United States Infantry, and was then reassigned to the Thirty-seventh United States Infantry, stationed in Kansas. On January 10, 1867, he married Alice Blackwood, who later that year gave birth to a daughter, the Baldwins' only child.
In 1869 Baldwin was assigned to Col. Nelson A. Miles's Fifth United States Infantry. During the Red River War in the Panhandle (1874–75) he served as chief of scouts and fought in the first battle of Palo Duro Canyon, where he earned a captain's brevet on August 30. After the battle he commanded a group of four who rode to Fort Supply carrying dispatches, a journey known as Baldwin's Ride (September 7–10). On November 8, in leading an attack against a Cheyenne camp on McClellan Creek in Gray County in which he rescued two of the German sisters from captivity, he earned a second Medal of Honor. After the massacre of George A. Custer and his troops at the Little Bighorn in 1876, Baldwin was transferred with Miles's regiment to Montana, where they established Fort Keogh, near Miles City. On December 18, 1876, Baldwin commanded a detachment that dispersed Sitting Bull's camp at the head of Redwater Creek. At the battle of the Wolf Mountains on January 8, 1877, Baldwin rallied the troops in an assault against Crazy Horse and earned a brevet to major. He also participated in the Lame Deer expedition and the campaign against Chief Joseph's Nez Percés later that year. In 1879 he was promoted to captain. From 1881 to November 1885 Baldwin served on General Miles's staff as judge advocate of the Department of the Columbia. In 1884 he negotiated a solution to unrest on the Moses and Coleville reservations in Washington Territory. From November 1885 to 1890 he served with his regiment in Montana, North Dakota, Texas, and New Mexico. He joined Miles again in December 1890 and served in the campaign against the Sioux until the spring of 1891. He investigated the Wounded Knee tragedy of December 1890. From 1891 to October 1894 Baldwin was inspector of small arms practice for the Department of the Missouri, headquartered at Chicago. From October 1894 to May 1898 he served as agent at the Anadarko Agency in Indian Territory. In 1898 he was promoted to major and subsequently to lieutenant colonel of volunteers.
Early in 1900 Baldwin was promoted to lieutenant colonel of the regular army and assigned to the Fourth United States Infantry stationed in the province of Cavite on the Philippine Island of Luzon, where his troops captured hundreds of insurrectos, including Lt. Gen. Mariano Trias. Baldwin was promoted to colonel in the summer of 1901 and received his own regiment, the Twenty-seventh United States Infantry. He sailed to Mindanao, where his troops defeated the Moros at Bayan on May 2, 1902. Baldwin was promoted to brigadier general in June 1902. In February 1903 he was appointed commander of the Department of the Colorado, a post he held until his retirement in 1906. He was promoted to major general (retired) in 1915 but left retirement briefly to serve as Colorado's World War I adjutant general. Baldwin died of cirrhosis of the liver on April 22, 1923, and was buried at Arlington National Cemetery. In 1929 his wife published her memoirs of his career and of her life as an army officer's wife on the frontier.