From their website:
"Rocky Mountain Journal of Mathematics"Rocky Mountain Journal of Mathematics publishes both research and expository articles in mathematics, and particularly invites well-written survey articles."
A search in Math Reviews shows many articles in RMJM described as expository, either by the authors or by the reviewer. Often there is disagreement as to whether a paper is expository, which indicates the utility of having a journal that publishes both research and expository articles.
I am on the board of the Rocky Mountain Mathematics Consortium.
I have found it nearly impossible to write an expository paper that stays that expository. New results have a way of being found by authors who are trying to clean up proofs of existing results.