Hell On Wheel's Naomi Bohannon was played by Siobhan Williams during season 3 but here's why the character was recast in season 4.

The series Hell on Wheels gets its name from a town built for workers of the first Transcontinental Railroad in the United States. This little town was called Hell on Wheels. The dramatic show portrays the lives of the workers, prostitutes, surveyors and families living in Hell on Wheels at the time of the railroad’s construction and is filled with mystery, drama, and suspense.