I had Marilyn, and especially Andy, riding the L. My editor suggested that people from outside the Chicago metro area would understand better if I spelled it 'El.' So, I did. In Chicago, we use the shorter spelling, though. "L" comes from "elevated."
New York has a subway; Chicago does not. Some of the L lines run underground, though. This sometimes confuses tourists. Chicagoans think tourists confuse easily. The "loop," the center of Chicago's downtown, is named after the square of actually-elevated tracks which runs around it. During rush hours, the Evanston train runs locally in Evanston then runs express to the near north side, and then runs locally around the (actually elevated) Loop. The rest of the day, Evanstonians have to change at Howard station (above Howard Street) to the normal Chicago L (which runs underground while it's traversing the Loop).