Silas Colgrove was born on May 24, 1816 in Woodhull, New York. Before the war he lived in Winchester, Indiana, serving as an attorney, state prosecuting attorney and in the Indiana House of Representatives from 1856 until the outbreak of the war.

At the beginning of the war he became a captain in and then lieutenant colonel of the 8th Indiana Infantry, which served its three month service in West Virginia, including the Battle of Rich Mountain.

On August 30, 1861 he became colonel of the 27th Indiana Infantry Regiment. The regiment spent the winter of 1861-62 in Frederick, Maryland, then fought in the Shenandoah Valley Campaign at Front Royal and First Winchester.

Colgrove had his horse killed in the Cornfield at Antietam, and his regiment lost nearly half the men, but he was himself unwounded. Colgrove was lightly wounded at Chancellorsville (where there is a monument to the 27th Indiana) on May 3rd, 1863, but returned to command the regiment at Gettysburg (where there is another a monument to the 27th Indiana), where he temporarily took command of the brigade. Receiving muddled orders, he launched a disastrous attack across Spangler Meadow, and was again lightly wounded.

Colgrove went west with the 12th Corps that fall, and was again wounded, this time seriously, on July 20, 1864 at Peach Tree Creek. After the fall of Atlanta the survivors of the 27th Indiana were transferred to the 70th Indiana. Colgrove served as president of the Indiana Treason Trials Commission for the remainder of 1864, and resigned his commission on December 30th.

After the war he returned to Winchester, becoming President of the Cincinnati, Fort Wayne & Grand Rapids Railroad, and was elected circuit judge for Randolph and Delaware Counties from 1865 to 1873.

In 1888 Colgrove was offered a position in the Pension Office and moved to Washington D.C. He resigned for health reasons in 1893. He died on January 13, 1907 in Lake Kerr, Florida.