Armageddon 2419 A.D. - by Philip Francis Nowlan

Armageddon 2419 A. D. features the introduction of Buck Rogers, the famous sci-fi adventure hero of early comics and radio shows. Originally published in Amazing Stories in 1928, this novella was later combined with Nowlan's sequel, The Airlords of Han, and re-published under this same title in the 1960s. In it we follow Buck Rogers and his mysterious transportation to far-future America. The land was conquered by the evil Han Empire centuries ago, and the local Americans, scattered into competing gangs, are now starting a rebellion.
Buck meets the leaders of one of the gangs and is swept up in the events.