The elevated train tracks that run through the city of Chicago and into surrounding neighborhoods is referred to as the "L" by locals and visitors alike. It is one of Chicago's features that is closely identified with, as it has been a prominent part of the city for more than 100 years. Since 1897, it has expanded into one of the country's largest public transportation systems, and now 1.6 million rides are taken on the train on an average weekday. Not only does it serve as a convenient way to get from one place to the next, but is also one of the best ways to see Chicago and learn about its dynamic history. So take a ride on the "L" and check out some of these historical stops along the way.

The Loop

Originally, the city was served by a massive street car and motor coach system, but it only worked locally and created more street congestion. So, city planners decided to elevate the tracks above the street in 1897, creating what is now known as The Loop, the 1.79-mile circuit of the train that forms the hub of the Chicago Transit Association (CTA). It is historically significant for joining all the different train lines in the late 1890s, giving people a common terminal downtown.

Many of the current stops deposit riders close to some of the most impressive buildings in the city. Your group can easily hop on the train at State & Lake, one of the last stations in the Loop to retain most of its original features, and take the Brown, Orange, Green, Pink or Purple line. (Note: The Brown, Pink and Orange lines make a full loop; the Green line only runs along the Eastern and Northern sides of the Loop.)

There are a number of impressive and historical attractions in the Loop, it's difficult to pick which ones to visit. Here are just a few suggestions to get you started:

The Rookery: An historic landmark located on LaSalle Street, the Rookery was completed in 1888 by architects Daniel Burnham and John Root. In 1905, Frank Lloyd Wright was commissioned to update the light court.

Union Station: Just a few blocks west of the Loop, Union Station is Chicago's major railroad station and opened in 1925. Designed by Daniel Burnham, Union Station is most well known for the ornate "Great Hall," with a vaulted skylight, statuary and connecting lobbies, staircases and balconies.

Willis Tower: Towering above the streets of Chicago, Willis Tower (formerly known as Sears Tower) is a prominent feature of the city's skyline. It was completed in 1973, and, at the time, was the tallest building in the world.

The Chicago Theatre: Opened in 1921, the Chicago Theatre was the first large movie palace in America and was built in French Baroque style. The "C-H-I-C-A-G-O" marquee is a major symbol of State Street and the city, and is a landmark in itself.

Famous Architecture to the West

The Green Line, originally known as the Lake Street "L" in 1893, extends both south and west of downtown. The western stretch of the track takes riders out to Oak Park, one of the most architecturally significant regions of the city. Tour groups can board the line in the loop and get off at the Oak Park stop, where they will be within a few blocks of some major attractions:

Frank Lloyd Wright Home and Studio: This structure served as the home of Frank Lloyd Wright and his family between 1889 and 1909. It is located in the Frank Lloyd Wright-Prairie School of Architecture Historic District, which includes about 27 Wright-designed structures.

Unity Temple: A Unitarian Universalist church, Unity Temple, built between 1905 and 1908, is considered to be one of Frank Lloyd Wright's most important structures.

Ernest Hemingway Birthplace: The home where famous American writer Ernest Hemingway was born and spent the first six years of his life.

Baseball History off the Red Line

The Red Line, one of two lines that does not run on the elevated tracks in the Loop, runs north and south of downtown and is the busiest CTA rail line. The northern route takes riders through some of Chicago's classic neighborhoods and right past Wrigley Field, one of the oldest ballparks in the country.

Tour groups can get off the train at Addison, where they will find Wrigley just steps from the station. The field, nicknamed "The Friendly Confines," was built in 1914 and has served as the home of the Chicago Cubs since 1916. Between 1921 and 1970, it was also home to the Chicago Bears football team.

After a quick tour through the stadium, your tour group can explore the surrounding residential area, known as Wrigleyville, which contains numerous bars, restaurants and other establishments.

IIT & Bronzeville to the South

Just off the south branch of the Green Line are the Illinois Institute of Technology (IIT) and the Bronzeville neighborhood. Groups can get off at the 35th-Bronzeville-IIT stop and explore some extremely significant areas of Chicago.

IIT, a research university, was formed in 1940 when the Armour Institute of Technology and Lewis Institute merged. What sets this school apart is the fact that German architect Ludwig Mies van der Rohe designed the campus. He created a spacious 120-acre campus at its current location, and most of his buildings were completed in the 1940s.

Bronzeville acts as a living monument to African-American culture. It has been home to a number of famous people, including legendary singer Louis Armstrong, civil rights activist Ida B. Wells, and the first African-American woman pilot Bessie Coleman. Some attractions worth visiting are the Stephen A. Douglas Tomb, The Victory Monument and the DuSable Museum of African American History.

Laughs off the Brown Line

The Brown Line, originally known as the Ravenswood branch, was first opened in 1907 and runs through the northwestern neighborhoods of Chicago. Just off the Sedgewick stop, your tour group will discover where improvisational theatre began. The Second City was formed in 1959 and was the first on-going improv theater in the U.S. It has since expanded to other cities, has produced television shows and has become a starting point for comedians, awarding-winning actors and directors.

Second City is located in the historic Old Town neighborhood, which features a number of boutiques, restaurants and bars along Wells Street. Also nearby is Tony Award-winning theatre company, Steppenwolf Theatre Company, founded in 1974.