Here is an interesting story out of the News-Sentinel (Fort Worth, TX) about a woman named Helen Newton who amassed one of the largest private collections of editorial cartoons over the span of 44 years (1939-1983) as a politically active letter writer.
The collection includes several Pulitzer Prize winning artists. Here are a few that were mentioned by name in the article: Bruce Shanks of the Buffalo Evening News, Tom Little of The Tennessean, Cecil Jensen, Ross Lewis of the Milwaukee Journal, John Fischetti, Chicago Daily News, Dick Locher, Chicago Tribune, Paul Szep, The Boston Globe, Charles Brooks of the The Birmingham News.
It notes that they were all given to her simply by asking.