Complex sentence: After the Triborough Bridge opened in 1936, it spurred the conversion of both islands to parkland, and soon thereafter, the city began filling in the passage between the two, to expand and connect the parks on each island.
Split into simpler sentences: After the Triborough Bridge opened in 1936, it spurred the conversion of both islands to parkland. Soon thereafter the city began filling in the passage between the two, to expand and connect the parks on each island.