Complex sentence: This work also was given to USACE, the only formally trained body of engineers in the new republic; during the first half of the 19th century, West Point was the major and for a while, the only engineering school in the country.
Split into simpler sentences: This work also was given to the Corps of Engineers, the only formally trained body of engineers in the new republic. During the first half of the 19th century, West Point was the major (and for a while, the only) engineering school in the country.