The full line is scheduled to open in 2025 and is planned to span 18 miles (29 km) from west to east and serve twelve stations in Downtown Seattle, Mercer Island, Bellevue, and Redmond.

The Eastside suburbs underwent rapid development into bedroom communities after the 1940 opening of the first Lake Washington floating bridge, which replaced a cross-lake ferry system as the main connection to Seattle.

[11][12] The proposal, funded with federal grants, was put to a public vote as part of the Forward Thrust referendums in 1968 and 1970, requiring a 60 percent majority in order to use increased property taxes.

[15] A transit element for the new floating bridge was requested by the Puget Sound Council of Governments and a group of municipal leaders from Seattle and the Eastside, seeking to avoid additional traffic.

[22] A work group, known as the Joint Regional Policy Committee, drafted a transit plan in March 1993 that conceived of a 105-mile (169 km) rapid rail system with a line between Seattle, Bellevue, and Redmond served by through-trains from Snohomish County.

[36][37] The final Trans-Lake Washington Study, published in 2002, recommended further development of a high-capacity fixed transit system on Interstate 90 to supplement a new floating bridge carrying State Route 520.

[44] The $3.9 billion light rail project, named "East Link", would be part of the next regional transit ballot measure and run from Seattle to Bellevue, the Microsoft campus, and downtown Redmond.

[50] The $18 billion plan projected that light rail trains would reach Bellevue in 2020 and Overlake Transit Center in 2021, and also included preliminary engineering for an eventual extension to downtown Redmond.

Using the results, which matched those from an earlier computer simulation, WSDOT concluded that the bridge could carry the weight of light rail trains after minor changes to sections of the transition spans were made during construction.

The panel identified 23 issues, including stray currents from the electrical system that could cause corrosion, the weight of the tracks and catenary on top of the deck, the design of the expansion joints, and a needed seismic upgrade for the bridge.

[57][58] Sound Transit authorized a $53 million budget for preliminary engineering work on the floating bridge segment in 2011, contracting out to a team led by Parsons Brinckerhoff and Balfour Beatty.

[66][67] Days later, Freeman re-filed the lawsuit in the Kittitas County Superior Court, naming Governor Christine Gregoire and Secretary of Transportation Paula Hammond as defendants.

[71] The city council voted to suspend development permits for light rail construction during the dispute; Sound Transit responded by seeking their own legal action to prevent the suspension, which was believed to be unlawful.

[72][73] A settlement was reached in June that allowed for the permits to be unsuspended in exchange for a Sound Transit payment of $10 million to mitigate traffic congestion and parking shortages expected to be caused by the closure of South Bellevue Park-and-Ride.

[76] The Sound Transit Board divided the line into five segments and identified 19 total potential alignments, including tunnel routes in Downtown Bellevue favored by the city's government, that were studied in the project's draft environmental impact statement in 2008.

[83][84] The composition of the Bellevue City Council was changed later in the year, with candidates backed by light rail opponent Kemper Freeman winning a majority in the November election.

[85][86][87] New councilmember Kevin Wallace proposed the "Vision Line", an elevated alignment that followed Interstate 405 and the Eastside Rail Corridor, with its downtown station connected by skybridges and moving walkways.

[93] The Sound Transit Board made the revised tunnel and South Bellevue alignment its new preferred route in April and requested further study into the impacts of rail construction in the Surrey Downs area.

[101] Sound Transit released its supplemental draft environmental impact statement in November, finding that the B7 alternative would be costlier to construct and require more wetland mitigation and displace more businesses.

[104][105] A group of fourteen business executives representing Boeing, Microsoft, T-Mobile USA, and Symetra, among others, sent a letter to the Bellevue city council in May requesting it to cooperate with Sound Transit and expedite the planning process.

[114][115] After the release of the study, high-level talks with Sound Transit were initiated by a delegation of Bellevue officials, including city manager Steve Sarkozy and councilmembers Degginger and Wallace.

[127] Sound Transit initiated design work on East Link in early 2012, commissioning a cost-savings analysis for the Bellevue segments to find elements where project costs could be reduced.

[129][130] Bellevue proposed an additional design change for the 112th Avenue corridor, moving the planned elevated flyover for trains into a trench under the raised road, after Surrey Downs residents complained of the potential visual and noise impacts.

[132] After the publication of the final cost-savings analysis in September, the Sound Transit Board and Bellevue city council voted to endorse the proposed design modifications to the downtown station, 112th Avenue crossing, and Winters House trench.

[133][134] The design modifications to Bellevue Way and 112th Avenue were opposed by residents of the Enatai and Surrey Downs neighborhoods, who claimed that the changes would restrict road access and lower property values and quality of life.

[144] In July 2014, Sound Transit selected a former rail yard located west of the Spring District and its station as the site of the project's 25-acre (10 ha) satellite operations and maintenance facility.

[147][148] After negotiations with the city, the design of the facility was amended to add 1.6 million square feet (150,000 m2) of commercial and residential development on part of the shrunken yard, and Sound Transit was asked to improve nearby pedestrian and bicycle connections.

[181] Light rail service was anticipated to begin in June 2023, but was delayed after a series of concrete structures, mainly over 5,455 plinths under the tracks on the 4-mile (6.4 km) Interstate 90 segment, were found in early 2022 to be in need of replacement or reinforcement.

[185][186] Balducci, several Eastside mayors, and other leaders endorsed a plan in 2022 to open a truncated Bellevue–Redmond version of the 2 Line in 2023 to serve local trips while awaiting the completion of the Seattle–Bellevue section with its extended timeline.

Trains reach Wilburton station, on the north side of Northeast 8th Street, and follow the Eastside Rail Corridor while descending to ground level near Lake Bellevue.