npr:
theoinglis:
The Evolution of the London Underground Map;
Above left to right - 1908, 1908, 1910, 1911, 1927, 1933, 1937 and the present day. (Old maps are from here)
Before the development of the iconic diagram style map in 1931 the tube map was constantly changing, never sticking to a consistent style. Some maps showed what was going on overground too and most of them attempt to be geographically correct, showing the curves and turns of the lines. By 1927 the map has become much clearer and easier to follow.
The problem was that the train lines were getting longer and this made it impossible to fit everything into one map. Keeping it geographically accurate would have meant that the centre became smaller and harder to read, and the centre is the most densely packed and most important part. In comes Harry Beck in 1931, inspired by electronic circuit diagrams he had the idea of scrapping geographical accuracy and making all lines straight with only 45 and 90 degree angles. Design history was made and the map has barely changed since, becoming an icon and one of the easiest to use maps in the world!
Interestingly some people think the map should be more geographically correct once again, have a look at this article for more on that. Personally I dont think the tube map needs changing. But if they could include a seperate geographically correct version of the centre of London on the pocket tube map, people would see how close some stations are together and it would encourage walking. But the map itself, isn’t broke so why fix it!
You just gotta love London, right? —Wright
Treehugger posted a great link to the something about maps blog, whose author has developed maps of river systems in the style of urban transit maps. The specific inspiration is the famous London Underground map developed by Harry Beck (the first edition of that map is below).

This map has been very influential in how other public transit systems are mapped. Chicago’s CTA train system is a direct descendant:

Daniel P. Huffman, the author of “something about maps,” has made maps for several river systems. Below is his map of the Mississippi River, and its tributaries:

I really like how these look. The information is much easier to grasp in this form than in a more precise representation. The most basic information: where the water begins, its general direction, and where the water ends are all communicated.
One of the best ways I’ve seen this illustrated is with the geographical representation of the London Underground. Compared to the Underground map featured above, the current subway system actually looks more like this:

This is much harder to interpret at a glance (which, let’s be honest, is what most subway travelers do) than the design aesthetic utilized in the Underground map. Applying that sort of thinking to a river map is just brilliant.

Pruned has a fascinating post about the usage of public park space for Cold War Missile Defense. All of these stations are no longer operational, of course, but some of these images are incredibly evocative. Imagine going for a stroll along the parks at Montrose Harbor, only to see a readiness drill in action, as shown in the photo above. It would certainly pull you out of your daydream—or maybe spur daydreams of a different sort.
These stations were placed all over the metro Chicago area, and at one point were capable of shooting missiles with nuclear payloads:

Head over to Pruned for more details on this lesser-known facet of Chicago’s history.