The Bronx River Parkway was the highway that opened up Westchester. It had been begun in 1906 as part of the project to clean up the Bronx River, which had become a badly contaminated eyesore by the turn of the century. In the process of building the parkway, the Bronx River bed was cleaned and dredged, 30,000 trees and 140,000 shrubs were planted, and paths and benches for the public were set among the trees and lakes. When it opened in 1925 the Bronx River Parkway immediately. drew worldwide attention to Westchester County.

The Bronx River Parkway was followed by the Saw Mill River Parkway, the Hutchinson River Parkway, the Taconic Parkway, and the Cross County Parkway, all completed by the 1930s. The scenic beauty of Westchester's parkways is still fresh fifty years later. The next major road construction did not take place until the 1950s and 1960s, when the interstate expressways and thruways were built.

The parkways brought many young, middle-class executives and professionals to Westchester to buy new homes being erected on old estates. The prosperity of the post-war period put cash in the pockets of many young families. They invested in real estate, which rapidly increased in value. Buying a home became the goal of everyone who could afford it.

Transportation was developed to accommodate the growing population. Local roads were paved, traffic regulations developed, and traffic lights installed. As the roadways improved, buses replaced the old trolley system. The Toonerville Trolley of Pelham made its last run in 1937; the Westchester bus system had replaced it.