Henry Augustus Cornwall was born on November 16, 1843, in Portland, Connecticut, to Andrew Cornwall and Elizabeth Whitmore. His father was a farmer who owned $6,000 of real estate and $2,000 of personal property by 1860. Cornwall grew up and attended school in Portland, but he abandoned his studies to enlist in the Union army on August 4, 1862.
He mustered in as a private in Company D of the 20th Connecticut Infantry on September 8. The regiment took part in the Battle of Chancellorsville, the Battle of Gettysburg, the Atlanta campaign, the March to the Sea, and the Carolinas campaign. He was reportedly an “excellent soldier, brave and faithful, seldom absent from duty, and his record is unsurpassed.” He was promoted to corporal on October 28, 1863.
He remained fiercely loyal to the Union, and he urged his family to vote for Republican candidate William Buckingham in the gubernatorial election of 1863. In February 1863, he emphasized that he “would like to come home but not untill after an honerable peace. I think that is what every soldier in the Army of the Potomac would tell you if you asked him.” In April 1865, he celebrated the news of General Robert E. Lee’s surrender, writing, “Hurrah for the old Union and flag long may it wave. If we can wipe out the Rebellion before or by the expiration of our term of service I shall be satisfied and will not complain.” Lincoln’s assassination, however, “entirely changed the feelings of this army to all Rebels in arms,” and they stood “ready with willing hearts and hands to obey the commands of our new President for the further suppression of the Rebellion and the punishment of traitors.” He mustered out on June 13, 1865.
He returned to Connecticut after the war. He attended business college and briefly worked for the Chase Lumber Company in Hartford, Connecticut. He returned to Portland in the late 1860s and accepted a position with the Middlesex Quarry Company. He married Gertrude Shepard on November 3, 1869, and they apparently had no children. By 1870, they owned $2,500 of real estate and $300 of personal property.
According to one local writer, he had a “singularly successful and honorable career in the stone business, gradually rising from one position to another.” He became one of the town’s “leading business men.” He travelled extensively throughout the United States and Canada. He was elected to the state legislature in the early 1890s. He applied for a federal pension in April 1890 and eventually secured one. He died of “paralysis of the stomach” in Providence, Rhode Island, on September 17, 1898.