Complex sentence: After the 1973 creation of the landmark district, primarily above 7th Avenue, the rate of gentrification was sped up, and throughout the 1970s, the area saw an influx of young professional couples.
Split into simpler sentences: After the 1973 creation of the landmark district, primarily above 7th Avenue, gentrification began to take off. Throughout the 1970s, the area saw an influx of young professional couples.