Central Park South has long been a reservoir of apartment-house construction, the expansive north views as attractive in the 1870s as they are now. The sweep of its history runs from the long-gone Bradley of 1877 to the modernist 240 Central Park South of 1940 — by way of the original Plaza Hotel of 1882 and the artistic Gainsborough of 1908. But as it turns out, it took awhile for developers to arrive at a full appreciation of Central Park South’s dazzling prospect.