A northbound Green line train exits the famed Chicago Loop "L" at Lake and Wells STs, site of Tower 18 and heads west over Lake Street, the only "L" route in the city entirely built over a street. Except for the downtown area and east 63rd street, Chicago "L"s are all built on private property, either lots strung together or on a strip of land at the back of lots alongside the alley. Reason for this is a state law that says an "L" had to get the consent of 51 % of the property owners to build over the street. It was cheaper to buy the land than to bribe property owners. Only exception was the downtown areas...there land was too expensive, so bribery prevailed there.