John Irvin Gregg John Irvin Gregg ( July 19 , 1826 – January 6 , 1892 ) was a career U . S . Army officer . He fought in the Mexican - American War and during the American Civil War as a general officer in the Union army . Early life and career . John Irvin Gregg was born in Bellefonte , Pennsylvania , the grandson of Andrew Gregg ( a U . S . Senator from Pennsylvania ) and a cousin of future Union general David McMurtrie Gregg . He was also related to Pennsylvania governor Andrew Gregg Curtin . Gregg served in the " Centre Guards , " a Centre County militia unit , as a lieutenant . During the Mexican - American War , he enlisted as a private in the 2nd Pennsylvania Infantry on December 29 , 1846 , and was mustered out of the volunteer service on May 6 , 1847 . He then received promotions to first lieutenant as of February 18 , and to captain as of September 5 , both in the 11th U . S . Infantry , serving as a recruiting officer . He was honorably discharged on August 14 , 1848 . He then entered the iron industry with the firm Irvin , Gregg & Co . , owned by family members . He married Harriet Marr , the daughter of a local Presbyterian minister and schoolteacher . They had two sons , Irvin and Robert . Civil War service . When the Civil War broke out , Gregg was commissioned a captain in the 3rd U . S . Cavalry on May 14 , 1861 . He then joined the volunteer army in June as a captain in the 34th Pennsylvania Infantry . He resigned soon afterward to accept a commission in the regular army as a captain in the 6th U . S . Cavalry . On November 14 , 1862 , Gregg was promoted to colonel of the 16th Pennsylvania Cavalry . He then commanded many different cavalry brigades in the various reorganizations of the Army of the Potomac . He led the Third Brigade at the battles of Chancellorsville and Gettysburg in a division commanded by his cousin David Gregg . In October 1863 , he earned another brevet to lieutenant colonel in the regular army for the Battle of Sulphur Springs . He was wounded at the Second Battle of Deep Bottom and won a brevet again on October 7 , 1864 to full colonel in the regular army . He was promoted to brevet brigadier general of volunteers on August 1 , 1864 , for gallant and meritorious service in the engagement and defenses of Richmond on the Brock Turnpike and at the Battle of Trevilian Station . On April 7 , 1865 , Gregg was slightly wounded at the Battle of Sayler ' s Creek , captured the next day north of Farmville , Virginia , and was released two days later . Near the close of the war , Gregg was appointed a brevet major general in the volunteers and brevetted to brigadier general in the regular army , both effective March 13 . He briefly was in command of the Cavalry Corps , Army of the Potomac from February 10 to February 24 . Gregg was mustered out of the volunteer service on August 11 . Postbellum . After the end of hostilities Gregg remained in the Army . He was named colonel of the 8th U . S . Cavalry on July 28 , 1866 , a position his cousin David McMurtrie Gregg had desired . He then reported for duty at Camp Whipple in the Arizona Territory . He led a series of expeditions against Indians into the Mojave Desert . He was sent to the New Mexico Territory , where he commanded Fort Union from 1870 to 1872 , and led efforts in that region to pursue and subdue the Apache . In 1872 , he led a reconnaissance expedition to survey and map the Texas Panhandle . Gregg retired from active service on April 2 , 1879 . He died in Washington , D . C . , and is buried in Arlington National Cemetery in Virginia .