I haven't seen the Cecil B DeMille western epic THE PLAINSMAN (1936) in something like forty years, and it was not readily available on streaming. But there was a mediocre TV remake in 1966, and I wasted a little time sussing that out.
The entirely fictional story brings together western legends, Wild Bill Hickock, Calamity Jane and Buffalo Bill Cody, respectively played by Don Murray, Abby Dalton and Guy Stockwell. However, in contrast to at least two of my "western legend crossovers" explored here and here, both versions of PLAINSMAN are null-crossovers, because in real history Wild Bill was associated in various ways with both Calamity and Buffalo Bill. Since they have that real-life connection, even the most absurd fictional story about the three of them does not count as a crossover.
Incidentally, the '66 PLAINSMAN is awful in every way, except that at the end Leslie Nielsen shows up playing the non-legendary (in my book) historical figure of General George Custer.