He graduated from the University of California at Los Angeles in 1965 and worked for six years as chief medical illustrator at Rancho Los Amigos Hospital, a large teaching hospital affiliated with the medical school of The University of Southern California.
In 1967, while still working as a medical illustrator, Auth began doing political cartoons. He first drew a single cartoon each week for Open City, a Los Angeles weekly. After a year, he began creating three drawings weekly for the UCLA Daily Bruin. Those cartoons were used widely in other college newspapers. In 1971, The Philadelphia Inquirer hired him as staff editorial cartoonist, and he is currently a member of its editorial board.
Auth has won several awards, including the Pulitzer Prize for editorial cartooning and the Sigma Delta Chi Award for distinguished service in journalism.
Auth's work appears five times a week in The Philadelphia Inquirer. He and his wife, Eliza, have two children.