In Boston and New York City, a "brownstone" is understood to be a terraced house (rowhouse) clad in brownstone. These brownstone apartments typically have stairways which lead from the sidewalk to a second-floor apartment entrance, a design originally intended to avoid bringing in the mud and horse droppings commonly found at street level, a problem that existed when these apartments were built and horses roamed the streets. Boston's brownstones are abundant in the Back Bay neighborhood and along Commonwealth Ave, where many have been converted to shops or apartment-style housing. Most were built as luxury townhouses during the late nineteenth and early twentieth century. New York City brownstones tend to be found in certain older neighborhoods, which are perhaps most common in Brooklyn. For example, the neighborhood of Bedford Stuyvesant has the largest inventory of brownstones in the entire City of New York, followed closely by Park Slope. Many brownstones have been renovated in recent years, leading to (and/or as a result of) gentrification in areas like Park Slope, Bedford Stuyvesant and Fort Greene.