Gunsmoke was one of the best radio dramas ever made. Further, it holds up well today. The show was created by Norman Macdonnell and John Meston, and ran from 1952 to 1961, overlapping with the television series. The radio series dealt with a number of topics too edgy for the television series, including drug addiction and prostitution. Another notable difference about the radio series is that the good guys did not always win.
William S. Paley, chairman of CBS, was a fan of Raymond Chandler's detective works, and came up with the basic idea. His concept was a hard-boiled adult western, similar to Chandler's hard-boiled detective works. The project was partially developed, then shelved, and came back to life a few years later when Macdonnell and Meston discovered it, and decided to run with the idea.
Here is an audio file of the first show, "Billy the Kid". It aired on June 26th, 1952 (when, incidentally, I was about to celebrate my first birthday).
Another treat for Gunsmoke fans in the Internet Archive is a series of comic books based on the television version of the series. The comics available available here are from a series run by Dell from 1958 to 1962. Be sure to click on "full screen" to make the comics large enough to read.
The Internet Archive contains an overwhelming number of treasures like this. I hope you enjoy them.