Try this (on PC at least, maybe not app):
From the main classified page
click on "Browse by Category - Trailer for sale"
Then scroll down the page till you see the map.
Use the page numbers on the bottom to see the locations of the trailers for sale
, 12 at a time.
Or choose a US state on the left to see just the trailers for sale for that state on the map. You can even further refine by city then if you wish, but with the few ads there are it seems pointless.
I dont know why its limited to 12 but there seems to be no way to display more on one page.