While it may not look like it from our perspective, at the time, KID COLT OUTLAW was Marvel's most popular Western series, with the character himself appearing in more than ten different titles over the life of his magazine.  Beginning in 1948, the title ran for twenty years before taking a hiatus, then returned to run another ten, finally ending in 1979 along with all the remaining Marvel Westerns.  By that time, no title was featuring new material any more.