Complex sentence: Nevertheless, Seward remained on excellent personal terms with southerners such as Mississippi's Jefferson Davis and gave dinner parties, where those from both sides of the sectional divide mixed and mingled, that were a Washington legend.
Split into simpler sentences: Nevertheless, Seward remained on excellent personal terms with individual southerners such as Mississippi's Jefferson Davis. His dinner parties, where those from both sides of the sectional divide mixed and mingled, were a Washington legend.