Stories about the Pony Express were published in The Victor and Hornet comics.
See The Victor (title:- Tales of the Pony Express, issues 2 - 9; no stories in issues 10 or 11; 12-18; Victor annuals 1964 & 1965).
The Hornet (title:- Slade of the Pony Express, issues 1-19).
Writers:- The Victor & Hornet editorial teams.
Artists:- The Victor issues 2-9 artist not known; Peter Sutherland (Victor issues 12-17).
Victor annuals 1964, 1965 (artist Sutherland for both years).
The Hornet - artist not known.
Main cast:- J. A. Slade and various Pony Express riders (Victor and Hornet); Wal Loader (Hornet only).
Time period:- American West, mid-nineteenth century.
The Pony Express was an American mail service delivering letters, newspapers, packages and so on from St. Joseph, Missouri from the East side of America to Sacramento, California in the West, using fast horses and determined and honest riders. They promised and achieved to deliver items in ten days, covering a distance of 1,900 miles (3,100 km). The service lasted only for eighteen months (03rd April 1860 to October 1861), before being overtaken by the telegraph system. The Pony Express was the brainchild of William H. Russell, Alexander Majors and William B Waddell all of whom worked in the freighting business. The organisation to run this service was impressive.
Before a rider could join the company he had to swear an oath on a bible. This was at the behest of Alexander Majors who was a religious man.
Famous riders of the Pony Express included a young William Frederick "Buffalo Bill" Cody.
The Jack Slade that appears in the Victor and Hornet comics did exist in real life. (Although the Slade portrayed in the Victor was different to the Slade that appears in the Hornet. In the Hornet he had a running feud with Wal Loader, whilst in the Victor the Loader character was not mentioned and the stories featured a different Pony Express rider each week. As far as I can tell, all of them fictitious). Both comics did show Slade as a forceful, fiery character who would go to sometimes extreme lengths to keep the Express service going. This appears to what he was like in real life.
Joseph Alfred "Jack" Slade (22nd Jan. 1831 to 10th March, 1864), led an adventurous life serving with the US Army in the Mexican War, the freighting business, before working as a Superintendent for the Pony Express. Slade was also a gunslinger. Prior to joining the Pony Express Slade had shot and killed Andrew Ferrin, a subordinate who was hindering the progress of a freight train in May 1859. He was lynched by local vigilantes in March, 1864 after going on a drunken spree in Virginia City, Montana.
Cody mentioned Slade in his memoirs and recalled him as a wild character, but who never did Cody any harm.
The above information is from the Pony Express Wikipedia pages.
The following adventures of the Pony Express riders are from issues the Victor 2; 3; 14; 16; 18.
Below are two Pony Express / Slade stories from The Hornet, issues 13 and 19.