A. O. Granger was a Union private in the Civil War serving directly under General W. T. Sherman as his secretary. He rose to his station as a result of his high quality penmanship. During 1864 Union forces briefly camped in various locations around Cartersville including what became Granger Hill. Following the war he married Caroline Gregory, became a wealthy entrepreneur, mining engineer and amateur astronomer. He returned to Cartersville and purchased the hill where he had camped while in the Union Army.

He soon built a massive home of 28 rooms named the Overlook, entered the local mining industry, became a valued member of the community, entertained frequently and installed in his home the largest observatory and telescope in the southeastern United States. Following his death the telescope was sold to a traveling circus and was eventually purchased by the University of Texas at Austin with the observatory moving to Agnus Scot College in Atlanta. According to family oral history, Granger hosted General Sherman on his return visit to Cartersville under an alias name of “Mr. Smith” enabling him to conduct research for writing his memoirs. At the conclusion of Sherman’s visit the Granger’s hosted a coming out party to introduce him, but no one attended once invited guests saw the real name on the invitation.