One way to start would be to use the search engine in the upper right. Start by clicking on the coonskin logo in the upper left of the screen, then click in the search box and type in the key words, Fort Smith, then click on search.
Be sure and investigate the Fort Smith-Van Buren railroad pages on the web. These pages were originally compiled by Mike Condren and are now hosted by the Boston Mountain Chapter National railway Historical Society (NRHS). https://condrenrails.com/FSVB/FSVB-Railroad-Pages.htm