As New Yorkers mark the 150th anniversary of Central Park, it's worth noting how that 843-acre jewel influenced the rest of the country. For it launched the career of Frederick Law Olmsted, the father of American landscape architecture. It's hard today to imagine New York City without Central Park, Boston without the Emerald Necklace, Washington without the National Zoo or Rock Creek Park - all the work of Olmsted, or (in the case of Rock Creek Park) his son, Frederick Law Olmsted Jr., who carried on his work. Central Park's serene beauty is not the original landscape of Manhattan. That...