This timeline was put together by David Alpert from GreaterGreaterWashington of the evolution of the DC metrorail system. http://greatergreaterwashington.org/post.cgi?id=4835
The best part about this is watching how the system grew and expanded (and threatens to be curtailed due to finances) over the last 34 years. As you click through the timeline and watch the system grow, you can see how a lot of growth happens over very short periods of time. It's unfortunate when you compare this to the Baltimore system which grew very slowly, and still struggles with the best way to successfully expand service.
D.C.'s metrorail is a testiment to strong, consistent funding backed up by sound decision making, planning, and connectivity. The same cannot be said with Baltimore, where our funding has been much less, our planning being focused more on cheaper rather than most effecient, and our connectivity is lacking.
Anyone interested in putting together something similar for Baltimore?