Action Comics #1 in mid-grade is a $100,000+ book, Amazing Fantasy #15 in high grade is a $100,000+ book, and The Adventures of Obadiah Oldbuck, America's first comic book, 163 years old, much rarer than 2 the book referenced above, has a high Guide price of only $4,500.

Published in 1897, The Yellow Kid in McFadden's Flats is considered to be the first comic book, insomuch that it bore the phrase “comic book” on its back cover.

If you care about the combination of words and pictures in a pamphlet telling a story, it's The Adventures of Obadiah Oldbuck. If you care about the actual phrase “comic book,” it's The Yellow Kid in McFadden's Flats.

Comics have been in existence since the end of the 19th century, but it was after the depression that the popularity of newspaper cartoons expanded into a major industry. The precise era of the Golden Age is disputed, though most agree that it was born with the launch of Superman in 1938.