For me, season 4 will always be the standout.
"Since Delaney nearly caused the deaths of his crew by trying to tunnel into the hill, Cullen takes it upon himself to plot a line of track over it. In town, Naomi faces religious differences with Ruth and later tries to find comfort from her busy husband. Meanwhile, Campbell's men claims eminent domain of the saloon, causing proprietor Mickey McGinnes to put up a fight and land in jail. When Durant refuses to help, Cullen reminds Mickey of coming to this country with nothing yet finding a way to succeed. Eva, without a job, tries to prostitute herself to Durant, who gives her money simply because she is the only one in town that he respects. At Fort Smith, Aaron Hatch seeks evidence that the Swede is not Bishop Dutson. The Swede suggests asking Brigham Young to make the final judgement."