- September 1, 1990
- September 2, 1990 (This strip is used on the page for September 17 of the Dayspring Peanuts A Year's Worth of Smiles and Blessings Desk Calendar)
- September 3, 1990
- September 4, 1990
- September 5, 1990
- September 6, 1990
- September 7, 1990
- September 8, 1990
- September 9, 1990
- September 10, 1990
- September 11, 1990
- September 12, 1990
- September 13, 1990
- September 14, 1990
- September 15, 1990
- September 16, 1990 (The final appearance of Molly Volley)
- September 17, 1990
- September 18, 1990
- September 19, 1990
- September 20, 1990
- September 21, 1990
- September 22, 1990
- September 23, 1990
- September 24, 1990
- September 25, 1990 (The only direct interaction between "Pig-Pen" and Sally Brown)
- September 26, 1990
- September 27, 1990
- September 28, 1990 (The last panel of the strip is adapted in Snoopy Presents: One-of-a-Kind Marcie)
- September 29, 1990
- September 30, 1990 (This strip is adapted in the episode "Word of Mouth" from the 2014 French TV series Peanuts)
← August 1990 | October 1990 → |