Background
Coster was born in New York City, New New York
Coster was born in New York City, New New York
On April 17, 1861, just five days after the firing on Fort Sumter, he enlisted as a private in the 7th New York Militia, one of the first regiments to come to the defense of Washington, District of Columbia at the outbreak of the Civil War. He later enlisted in 1861 at age 24 as a first lieutenant in 12th United States Infantry. He served in Brigade General
George Sykes"s division of V Corps in the Seven Days Battles, being commended by his superiors for his conduct at the Battle of Gaines" Mill on June 27, 1862.
On October 8, 1862, Coster was named colonel of the recently organized 134th New York Infantry Regiment. By December 31, 1862, the regiment belonged to Colonel
Orland Smith"s 2nd Brigade of Major General Adolph von Steinwehr"s 2nd Division, XI Corps, Army of the Potomac.
Coster"s regiment participated in the Battle of Chancellorsville under Brigade
General Francis C. Barlow, who had been appointed brigade commander in place of Smith. During May 1863, Coster"s regiment joined the 1st Brigade, 2nd Division, under Colonel
Adolphus Buschbeck. When Buschbeck went on leave on June 10, Coster became brigade commander.
In that role he patrolled near Boonsboro, Maryland before marching to, Pennsylvania. Major General Oliver Otis Howard kept von Steinwehr"s division in reserve on the first day of the Battle of, July 1, 1863, positioning it on Cemetery Hill. When the Union right flank north of town began to collapse, Howard permitted von Steinwehr to send Coster"s brigade to cover its retreat.
These Union troops took a position just north of the town, where they were deployed in a brickyard.
The brigade was attacked by superior forces from the Confederate division of Major General Jubal Early. Coster"s brigade lost most of its 597 casualties in that action.
The remainder of the brigade spent the next two days supporting batteries on Cemetery Hill. Howard commended Coster and other senior commanders by name for their courage and devotion to duty in his report on
Later in 1863, Coster resigned his regimental command.
On May 18, 1864, he was appointed a provost marshal for the State of New York to serve the Board of Enrollment.
Coster resigned that position on April 30, 1865. Thereafter he lived in New York City. On February 28, 1882, he became a federal Pension Agent for the city, resigning effective December 1, 1885.
Coster died in New York City and was buried on December 26, 1888.
Coster Avenue, part of the Battlefield but within the town itself, has a brigade marker and three regimental monuments. A mural painting on the wall of a neighboring building commemorates the Confederate attack and Coster"s defense.
He was also a member of the Grand Army of the Republic.