[citation needed] MetroLink shares some characteristics of a light metro or rapid transit service,[10][11] including a largely independent right-of-way, a higher top speed, and level boarding at all platforms.

[11] Being a light rail network, but with sections of tunnels creating a separate right-of-way, MetroLink can therefore be categorised as a semi-metro system.

The 8-mile (12.9 km) Cross County Extension opened on August 26, 2006 and added nine stations from Forest Park-DeBaliviere to Shrewsbury, Missouri.

Citing repeated delays and cost overruns, Metro fired and then sued its general contractor, Cross County Collaborative, in the summer of 2004.

An additional $5 million in funding was provided by a public-private partnership including Washington University, BJC HealthCare, Great Rivers Greenway and Cortex.

[23] On June 15, 2019, MetroLink set its single day ridership record when over 100,000 people used the service to attend the parade after the St. Louis Blues won the 2019 Stanley Cup playoffs.

[26][27] The flood damaged nearly 5 miles (8.0 km) of track bed, two elevators, two communications rooms, three signal houses and destroyed two MetroLink vehicles.

[29] On July 31, 2023, Metro received $27.7 million in federal emergency disaster relief funding to help cover the cost of restoration.

[31] In 2023, Bi-State's board approved a memorandum of understanding authorizing the Metro team to plan and develop the Green Line expansion with the City of St.

[32] In May, Metro received a $196.2 million federal grant to purchase new light rail vehicles to replace the remaining SD-400 cars.

[33] Six months later, Bi-State's board approved a contract with Siemens Mobility worth up to $390.4 million for as many as 55 new S200 light rail vehicles with delivery expected to begin in 2027.

Entering St. Louis City at Skinker Boulevard, the line stops at the Delmar Loop station and its namesake entertainment district.

[40] The 24-mile (38.6 km) Blue Line alignment starts at the Shrewsbury-Lansdowne I-44 station in Shrewsbury, just west of the River des Peres.

It then proceeds in a tunnel underneath Interstate 64, continuing to the Richmond Heights station, which serves the Saint Louis Galleria shopping mall.

The Red Line continues south through Belleville, Illinois, to its terminus at the Shiloh–Scott station near Scott Air Force Base.

[45] In May 2023, Metro received a $196.2 million federal grant to purchase up to 48 Siemens S200 high-floor light rail vehicles to replace 25 of the oldest cars.

[46] Six months later, Bi-State's board approved a contract with Siemens Mobility worth up to $390.4 million for as many as 55 new light rail vehicles.

[58] That spring, Metro began rehabilitating the downtown subway tunnels,[59] including the Laclede's Landing, Convention Center, and 8th & Pine stations.

[60][61] Elsewhere, catenary wire, curve tracks, platforms, retaining walls, staircases, and system conduit are to be upgraded or replaced.

[64][65] In 2026, Metro expects to complete upgrades to the Supervisory Control Automated Data Acquisition (SCADA) and Public Address/Customer Information (PA/CIS) systems.

[67] In 2024, Metro Transit began adding turnstiles at all MetroLink stations as part of its $52 million Secure Platform Plan (SPP).

Stations will also receive a new fare collection system, more fences, passenger-assist telephones, and more than 1,800 cameras to be monitored at a center opened in November 2022 at Metro's Central Garage.

[70] In September 2023, Bi-State awarded a $6.4 million contract to Millstone Weber LLC for the first package covering four Illinois stations.

[79] In September 2023, Bi-State Development's board approved a 4-year, $18.9 million contract with the joint venture Northside-Southside Transit Partners to provide consulting services for the design phase of the project.