Here's some trivia about Lonesome Dove from www.imdb.com:

Originally written by Larry McMurtry in 1971 as a movie script. He intended John Wayne to play Woodrow Call, James Stewart to play Gus McCrae and Henry Fonda to play Jake Spoon, with Peter Bogdanovich directing. Wayne turned it down, and the project was shelved. Ten years later McMurtry bought the script back and wrote the book (on which the series was based).

Charles Bronson turned down the role of Woodrow Call

Robert Duvall was cast as Woodrow Call but then got the part of Augustus. James Garner was chosen next but bowed out for health reasons, and Jon Voight turned down the role, so Tommy Lee Jones was cast. However, both Garner and Voight would portray Woodrow Call in sequels.

The set of San Antonio street, at the Alamo, is the set built for Alamo: The Price of Freedom (1988). It was designed by Roger Ragland.

The Latin phrase, "uva uvam vivendo varia fit" that appears on the Hat Creek Cattle Company sign translates to "a cluster of grapes through living begets one grape," representing the synthesis of Larry McMurtry's tale as an American epic.

Virtually every major role from this film has also appeared in one of its sequels, and almost all of them have been recast, sometimes several times. In three cases, original cast member have been able to work with one of their successors. Timothy Scott reprised his role in the unofficial sequel "Return to Lonesome Dove" (1993) (mini), but died before production began on the official sequel, "Streets of Laredo" (1995) (mini). He was replaced by Sam Shepard, who had directed him in Silent Tongue (1994). Tommy Lee Jones was replaced in "Streets of Laredo" by James Garner, with whom he appeared in Space Cowboys (2000). Danny Glover was replaced in the prequel "Comanche Moon" (2008) (mini) by Keith Robinson, with whom he appeared in Dreamgirls (2006).

The set for Ogalalla, Nebraska, was originally a set built for Silverado (1985), which also starred Danny Glover.

For authenticity the producers decided to use real ranch horses in the movie. When the effect of "bullets" hit below Gus' horse, the response was genuine and Duvall was actually bucked off. Because it lent itself to the authenticity everyone desired, the cameras continued rolling and the scene was kept in the final cut.