If the Gulf oil spill was over New York, that is how big it would be. It is large enough to cover the entire states of Connecticut and Rhode Island. Without difficulty it could easily cover the entire Harlem Line: the original line, all the way to Chatham. Heck, it would cover all of Metro-North’s track!
This site is really great for visualizing how big this oil spill actually is. The map can put the spill over any part of the earth you are familiar with, so you can get a better idea. Crazy stuff.