As recorded on the 1850 U.S. Census, Andrews was born in the District of Columbia and later moved to Baltimore, Maryland.

His other commissions included the Maryland Governor's residence in Annapolis and the south wing of the U.S. Treasury Building in Washington, D.C.[1] Andrews' sister married Virginian Charles Marshall, who would become a key member of Robert E. Lee's staff during the war.

[2] In August of that year, the 31-year-old major was in charge of General Charles S. Winder's divisional artillery.

On August 9, at the Battle of Cedar Mountain in Virginia, a Federal shell exploded close by, which nearly disemboweled Andrews when fragments struck his right side.

Holding in his intestines with one hand and sliding from his horse, he fell to the ground and landed on his back.

Von Moltke, in turn, was so impressed with the wound and Andrews's bravery, he immediately agreed to sell the Confederacy the armaments they wanted.

Ironically, as Andrews was returning to catch a ship west, and before delivery was taken of the arms, the South surrendered at Appomattox (April 1865).