In 1848, for unknown reasons, mysterious happenings began to rise, demons stalking the night, people missing and never to be found, etc etc. Most took these for the simple hysteria but then something happened, the first rift opened. In 1856 in the swamps of Louisiana a horrible miasma is corrupting everything...and it's spreading.
Others saw this as an opportunity, placing bounties on the disgusting abominations that arose from these corrupted lands as well as using the lawlessness of deadlands (places affected by the rifts) to conduct illegal activities away from the eyes of law enforcement. So now you to have come to the first rift, let's see how long you last.