MetroLink is the light rail

Light rail

Light rail or light rail transit is a form of urban rail public transportation that generally has a lower capacity and lower speed than heavy rail and metro systems, but higher capacity and higher speed than traditional street-running tram systems...

 transit system in the Greater St. Louis area of Missouri

Missouri

Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...

 and the Metro East area of Illinois

Illinois

Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

. The entire system currently consists of two lines (Red Line and Blue Line) connecting Lambert-St. Louis International Airport

Lambert-St. Louis International Airport

Lambert-St. Louis International Airport is a Class B international airport serving Greater St. Louis. It is located approximately northwest of downtown St. Louis in unincorporated St. Louis County between Berkeley and Bridgeton. It is the largest and busiest airport in the state with 250 daily...

 and Shrewsbury, MO

Shrewsbury, Missouri

Shrewsbury is an inner-ring suburb of St. Louis, located in St. Louis County, Missouri. The population was 6,254 at the 2010 census.The city is home to the broadcast towers of KSDK- and KDNL-TV.-Geography:Shrewsbury is located at ....

 with Scott Air Force Base

Scott Air Force Base

Scott Air Force Base is a base of the United States Air Force in St. Clair County, Illinois, near Belleville.-Overview:The base is named after Corporal Frank S. Scott, the first enlisted person to be killed in an aviation crash...

 near Shiloh, Illinois

Shiloh, Illinois

Shiloh is a village in St. Clair County, Illinois, United States. A 2005 census recorded a population of 11,000.-Geography:Shiloh is located at ....

 through downtown St. Louis

St. Louis, Missouri

St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...

. The system features 37 stations and carries an average of 51,716 people each weekday.

A second line, the "Cross-County Extension," now known as the Blue Line, opened to the public .