Great Black Swamp
Mary was taken by the squaws northward along the Ohio River to the Wabash, which the Indians called the Wabashike. They waited there until the raid at Fort Jefferson was over and the braves had rejoined them. In Songbirds are Free, one brave in Mary's Shawnee tribe was killed at Fort Jefferson.
  From there, they went overland to the Great Black Swamp. Some accounts of Mary's capture have them living in Indiana during the first year of her captivity.
They crossed the Great Black Swamp en route to Fort Detroit, which was a British stronghold. Henry Hamilton, the Lieutenant Governor of Canada during the American Revolution, was based at Fort Detroit and was tasked with securing a land roughly the size of France. Because he had very few men, he enlisted the aid of the Indians, particularly the Shawnee. The British paid for every scalp and captive the Indians brought to them. Though Hamilton himself was captured by George Rogers Clark at Vincennes in 1779, the British soldiers continued to pay the Indians for scalps and captives.
  In Songbirds are Free, while crossing through the Great Black Swamp, Eagle Feathers, the chieftain of Mary's tribe, became ill with "swamp fever" which we now know as malaria. His condition was not unusual, as the area was known for heavy infestations of mosquitoes, though the population at that time did not know mosquitoes could spread malaria. He survived but his condition was weakened.

The Great Black Swamp is no longer in existence. In the late 19th century, it was drained and is now agricultural land. Once through this area, the tribe continued toward Fort Detroit...

Pictures above are from the George Rogers Clark National Historical Park at Vincennes, Indiana.