Complex sentence: He was an active participant at Philadelphia; and he helped achieve ratification by writing 51 of the 85 installments of "The Federalist" Papers, which to this day are the single most important reference for Constitutional interpretation.
Split into simpler sentences: He was an active participant at Philadelphia; and he helped achieve ratification by writing 51 of the 85 installments of "The Federalist" Papers. To this day, it is the single most important reference for Constitutional interpretation.