Complex sentence: When mining profits began to decline investment in Animas Forks was no longer justified and although mining made a brief 1904 rebound with the construction of the Gold Prince Mill, the town's mining days were nearing an end.
Split into simpler sentences: When mining profits began to decline investment in Animas Forks was no longer justified. Although mining made a brief 1904 rebound with the construction of the Gold Prince Mill the town's mining days were nearing an end.