As transportation routes were developed, making Brookline readily accessible to Boston, the population grew rapidly. In 1806, the Boston-Worcester Turnpike (now Route 9) replaced the old Sherburne Road (Walnut and Heath Street) as the Town's major highway and the main road west from Boston. Mill Dam Road was opened in 1821, extending Beacon Street into Brookline. This consummated Brookline's transition to the desirable commuter suburb that it is today.
The great nineteenth-century architect H.H. Richardson chose to live in Brookline as did his friend and colleague Frederick Law Olmsted. Considered to be the founder of landscape architecture in America, Olmsted served on the Town's Planning Board. Amy Lowell and John and Robert Kennedy were born here; physicians Walter Channing, George Minot, and William Murphy and Nobel laureate John Enders, horticulturist Charles Sprague Sargent, and musicians Serge Koussevitsky, Arthur Fiedler and Roland Hayes are some of the many notables who have been Town residents.