Newman and Redford in arguably the first modern Western
The gist of the story is historically accurate, with the movie starting in the late 1890s and ending with the outlaws' deaths in November, 1908, which means the picture encompasses about 9-10 years, although it seems more like a couple of years. In any case, this was a state-of-the-art Western when it was released and a huge success at the box office.
The production quality, tone and theme are comparable to 1967's "Bonnie and Clyde." It's a very 'modern' Western, arguably the first (although a good case could be made for 1967's "Hombre"), and therefore holds up well today, hardly seeming dated; that is, disregarding "Rain Drops Keep Falling on My Head," which plays during an interlude at the end of the first act. In spirit, the movie inspired future great modern Westerns like "The Missouri Breaks," "The Long Riders" and "Unforgiven," all superlative Westerns that don't seem to age as the decades pass.
While Redford was already appearing in significant movies, this is the one that shot him to stardom and he went on to star in notable Westerns like "Tell Them Willie Boy is Here" (which is laughable revisionism, if you know the true history), "Jeremiah Johnson" and the great "The Electric Horseman" (1979), the latter taking place in the modern day, of course. As for Newman, it's hard to believe he's the same actor that starred in the aforementioned "Hombre," as his character couldn't be any more different as Butch Cassidy, a fun-loving, witty train robber (in "Hombre" he's the opposite: a laconic, mirthless white man raised by Apaches).
Although the tone is similar to "Bonnie and Clyde," I don't think it's on the level of that film. I also don't understand the gushing it often receives. Yes, it's good, but at the end of the day, it's about two thugs who were on a collision course with premature death due to their own folly. Newman and Redford are entertaining as the pair, but it's hard to sympathize with fools who stubbornly insist on carrying on their idiotic thuggery even though they have the awesome opportunity to start a new life.
There are two sequels worth checking out: "Wanted: The Sundance Woman," a 1976 TV production starring Katherine Ross, which shows what happens to Etta after leaving the duo for America; and, especially, "Blackthorn," a 2011 release starring Sam Shepherd as Butch Cassidy in his old age in Bolivia, which presupposes that he somehow survived the ending of this movie.
It runs 110 minutes and was shot in Utah, Colorado, New Mexico, Arizona and California.