Towards the end of the 19th century, a large concentration of wealth was amassed by a very small percentage of businessmen. Nicknamed robber barons for their ruthless business practices and larger than life personalities, the Rockefellers, Vanderbilts, Morgans, Whitneys and Astors were just a few of the New York families that would build opulent mansions along 5th Avenue. Originally the southern portion of Fifth Avenue near Washington Square Park was reserved for townhomes of the wealthy, but with the construction of Central Park rich families began to migrate northward for larger properties to build larger homes. Central Park would become a catalyst for a building boom along 5th Avenue, and several families understood how Central Park would dramatically raise properties values along the eastern edge of the park. John Jacob Astor began to buy up large properties across northern Manhattan to later sell to other affluent families, thus creating a concentration of mansions that faced the park. In time Fifth Avenue between 59th and 95th streets would be nicknamed “millionaires row”. 
 
As the city grew, more density was required and land speculation created another building boom for taller buildings with luxury apartments. Many of these lavish and sprawling homes were replaced with taller luxury apartments with views of the park. Several mansions do survive and have been adapted into other uses. Many have been transformed into museums, and with the Metropolitan Museum of Art and the Guggenheim Museum also on the street, Fifth Avenue received another nickname “museum mile”.