Complex sentence: Monocacy, Maryland had been founded as early as 1730, when the Indian trail became a wagon road, but abandoned, perhaps due to the river's periodic flooding or hostilities predating the French and Indian War.
Split into simpler sentences: Monocacy, Maryland had been founded before 1730, when the Indian trail became a wagon road. It was abandoned, perhaps due to the river's periodic flooding or hostilities predating the French and Indian War.