Complex sentence: In 1786, Albany County was reduced in size by the splitting off of Columbia County, and in 1791, Saratoga County as well as Rensselaer County were split off from Albany County.
Split into simpler sentences: In 1786, Albany County was reduced in size by the splitting off of Columbia County. In 1791, Saratoga County (as well as Rensselaer County) was split off from Albany County.