One of my favorite classes in college was an American Studies seminar on Gilded Age New York City. It was probably the first time I started to get captivated by the city's history. One memorable class, my professor (whom I'm actually supposed to be eating dinner with this week) handed around an old picture postcard the kind tourists then and now buy to remember the various buildings of a city they've gone to visit, in this case New York. It was from around the turn of the last century, and yet the large majority of the "famous landmarks" were either unknown to us or had long ago disappeared from our present-day skyline. The take-away: New York, while it seems to be fixed in our minds, is forever changing, and will continue to change. It's a city driven by powerful individuals, whether politicians or business people, who have always wanted to shape a bit of the place after their own ideals or at least their profit goals. Yes, of course, there are certain things that remain much longer than others (Central Park, say), but around them, there is always change.
One great example of this is this panorama, excerpted above and available in full here, which apparently depicts lower Manhattan from around 1900. As far as the commenters on Gothamist and I can tell, it's a photo that was taken from the lower Hudson River, with the north at the left end and the south at the other. So few of the buildings are recognizable to today's skyline watchers. With some help from this site, it seems that the darker, almost Florentine building at the far right is the G.B. Post Produce Exchange, now replaced by Two Broadway, home of the MTA, and not far from the Battery and the old Customs House, just out of the frame. Toward the middle are the buildings of Park Row, former locus of the New York newspaper trade. Along the waterfront are docks labeled Pennsylvania Railroad. As for how far the image stretches to the north (left side), it's really hard to say, but I'm going to have to guess somewhere around Spring Street, where the Holland Tunnel was built two decades later. Missing from the picture, of course, is the infill land that would be used to create Battery Park City. Some of this is conjecture, so I'd be open to any disagreement over dimensions and buildings.