Complex sentence: After Dobson's Encyclopædia (published 1789-1798), it was the first significant American encyclopedia; although based on Brockhaus' "Conversations-Lexikon," it had significant added and rewritten material.
Split into simpler sentences: After Dobson's Encyclopædia (published 1789-1798), it was the first significant American encyclopedia. Although based on Brockhaus' "Conversations-Lexikon," it had significant added and rewritten material.