Complex sentence: Other reasons given were the advent of steam boats (which were not practicable above Augusta), and later, the rivers worked against the construction of railroads essential for economic life after 1850.
Split into simpler sentences: Other reasons given were the advent of steamboats (which were not practicable above Augusta). Later, the rivers proved to be obstacles to construction of railroads through the area, considered essential for the economic life of towns after 1850.