He established the Etowah Iron Company in Bartow County, had mining interests in South America, and was a business partner to Joseph M. Gazzam.

During the American Civil War, Granger was a private in the 15th Pennsylvania Cavalry Regiment, and became the secretary to General William Tecumseh Sherman.

Granger served as part of the March to the Sea, and wrote the papers for General Joseph E. Johnston's surrender in 1865.

[5] At age 16 on September 8, 1862,[2] Granger enlisted as a private in the 15th Pennsylvania Cavalry Regiment for the Union army during the American Civil War.

[2] Granger wrote in his memoirs that he was treated six weeks for typhoid fever at a hospital in Murfreesboro, Tennessee, as a result of the battle.

[6] Granger wrote the papers for General Joseph E. Johnston's surrender to Sherman on April 26, 1865, then kept the inkstand and pen as mementos of the occasion.

Granger constructed a railroad from the mine to the Etowah River 4 miles (6.4 km) away, where he also built a manganese processing facility.

In the same year, he was suspended as general manager of the Auer Incandescent Light Company in Montreal, amid charges that he forged power of attorney on customs documents for supplies imported from the United States.

[5] Granger married Caroline Dickson Gregory on August 15, 1870,[2][3] and subsequently lived in Philadelphia, Montreal, and Quebec.

[7] They lived at the west end of Main Street, later known as Granger Hill, and became involved in the social and cultural scene in Cartersville and Atlanta.

[3] Their home, named "Overlook", included twenty-eight rooms and the largest observatory and telescope in the southeastern United States.