Today in the history of the American comic strip: December 7

American cartoonists and writers may not have invented the comic strip, but some argue that the comics, as we know them today, are an American creation. Clearly, the United States has played an outsize role in the development of this underappreciated art form. 
 

12.7.1936: Frank Miller's Barney Baxter in the Air, an aviation strip, goes into national syndication.

12.7.1941: It’s a Girl’s Life (which later evolved into Teena) debuts. Created by Hilda Terry, It's a Girl's Life and its successor ran until 1966.
 
12.7.1970: Rube Goldberg dies in New York City at 87. A sculptor, author, engineer and inventor, he is best known for his cartoons depicting complicated gadgets that are designed to perform simple tasks. Goldberg is a member of the National Cartoonists Society Hall of Fame.

12.7.2006: Johnny Hart's B.C. draws criticism for defining infamy as "a word seldom used after Toyota sales topped 2 million." Hart made the remark on the 65th anniversary of the Japanese attack on Pearl Harbor, which President Franklin D. Roosevelt described at the time as a "day of infamy." 
 

Most of the information listed here from one day to the next comes from two online sites -- Wikipedia, and Don Markstein's Toonopedia -- as well as 100 Years of American Newspaper Comics, edited by Maurice Horn. Note that my focus is on American newspaper comic strips (and the occasional foreign strip that gained popularity in the United States). Thus, comic books and exclusively online comics are not included here.