All five options included a route running west to east, from Browne's Addition, through Downtown, to the University District, which is ultimately reflected in part of the City Line's final, single-line alignment.

[8] Public workshops and a series of meetings with stakeholders were held from 2010 through early 2011 to identify preferred mode and route alternatives for the new line.

[11] The City Line's final estimated development costs of $92.2 million are funded through a variety of local, state, and federal sources.

[14] STA was awarded its $53.4 million request from the Federal Transit Administration (FTA) Small Starts Grant in April 2019,[15] which would have fully funded the project when combined with the earlier allocation by the Washington State Legislature in 2015.

[18] In July 2023, the STA board voted to direct the unused local funds to the agency's next bus rapid transit project, Division Street BRT.

Major construction of the line's components, including roadway improvements along the route, supporting infrastructure, and boarding stations, began on May 1, 2020[21][22] and continued through 2021.

[23] Prior to start of this phase, Spokane Transit completed upgrades at some of its existing facilities that will ultimately enable and support City Line operations, including alterations to boarding zones at the STA Plaza,[24] reconstruction of the Spokane Community College Transit Center, and constructing a new garage[25] at STA's main campus that will house, service, and recharge the City Line's electric battery electric fleet when not in use.

The first phase, which concluded in May 2022, addressed infrastructure including roadway improvements, communications conduit, and building the concrete station platforms.

By the conclusion of the phase, Spokane Transit Authority estimated that it had put in more than 10,000 hours of testing to ensure as few issues as possible after launching the service.

[33] STA hosted simultaneous launch day celebration events in the Browne's Addition, Downtown/Riverside, University District, Logan, and Chief Garry Park neighborhoods with food and music.

The fare-free period was set to run from the service launch date of July 15, 2023, to Labor Day on September 4, 2023, in order to encourage use of the new route and for the community to see the new electric busses and Eastern Washington's first bus rapid transit line.

Spokane Transit announced plans to implement City Line's 7.5 minute peak headways the following year,[37] which ultimately commenced with the agency's January 21, 2024 service change.

The eastbound and westbound paths briefly converge in the core of Downtown at the STA Plaza, where passengers have the opportunity to connect to nearly every other route in the Spokane Transit network.

After passing through several stations, the City Line route reaches its eastern terminus at the Spokane Community College Transit Center, which provides riders transfer opportunities to other STA routes, a driver layover point, and rapid charging facilities for City Line's battery electric buses.

However, at left-hand boarding City Line stations, on-board cash payments are not possible due to lack of front door on the driver side of the bus.

[43] Spokane Transit planned to take delivery of the first of the buses in Q2 2021 for testing with the remaining 9 vehicles delivered toward the end of 2021, in time for the start of City Line operations in 2022.

[46] The initial fleet of buses utilized on City Line are equipped with batteries that have a 320 kilowatt-hour (kWh) capacity, enabling a driving range of 120 to 150 miles.

After the initial peak, buses connect to rapid chargers during 15-minute layover periods at the line's eastern terminus, Spokane Community College Transit Center, before beginning another route run.