Was having this discussion recently, and the earliest I (or anyone) could come up with was 1979’s Butch and Sundance: The Early Days. Were there any prequels released before this one?
May not be around for a while, so thanks in advance.
Sir Rhosis
There was Chinavillage and Chinahamlet.
The Nightcomers was made in 1972.
King Kong was made in 1933, and Son of Kong was also made in 1933. Mighty Joe Young was in 1949, Konga in 1961, King Kong vs Godzilla in 1963, King Kong Escapes and King of Kong’s Island (both in 1968), King Kong and APE in 1976, Queen Kong in 1977, King Kong Lives in 1986, and The Mighty Kong and Mighty Joe Young in 1998.
The case can be made that Mighty Joe Young shouldn’t be considered a sequel, but the others certainly can fall into the sequel category.
I like Kong.
I like him too but none of the movies you’ve mentioned are prequels.
The Good, the Bad and the Ugly, perhaps?
The Godfather II (1974), maybe?
The Scorpion King was set in ~5000BC - does that count? 
For those unfamiliar with the term, a prequel is a movie made after another movie sharing the same story line but which takes place before.
The first one remember seeing is the Butch and Sundance one mentioned in the OP. I’d be interested in knowing of any others.