St. Louis, like many cities in the mid-20th century, was a city full of streetcar lines. Unfortunately, the lines - featuring cars often built in St. Louis - were put out of commission, disassembled and paved over and our public transit options were lessened in the process. Along with the slow, gradual expansion of the Metrolink system in recent years, there's been a continuing conversation about adding streetcars to the public transit mix, with midtown St. Louis' Grand Center and the Forest Park-to-University City Loop areas the most-mentioned areas for this idea to work.
We should note that the University City Loop's not a far jump from America's Center via Metrolink. You'll be dropped off near the old Wabash Station, and from there, you'd want to travel west, down Delmar. That street's been cited as one of the 10 great streets in America and you'll see a visible amount of construction still taking place, especially in the eastern end of the block (which lies in the City of St. Louis), where the area's first hotel is being built.
We've embedded a few KETC video links lately, and this one's got some info on STL's streetcar past and (hopeful) future.