Editing Blue Line (CTA) (section)

{{Short description|Rapid transit line in Chicago}}
{{Use American English|date=May 2025}}
{{more citations needed|date=November 2024}}
{{Infobox rail line
| color                           = {{rcr|CTA|Blue}}
| name                            = Blue Line
| image                           = File:I-290 and UIC-Halsted station.jpg
| image_width                     = frameless{{!}}upright=1.35
| caption                         = A Blue Line train of [[7000-series (CTA)|7000-series]] cars leaving [[UIC&ndash;Halsted station]] on the Congress branch
| type                            = [[Rapid transit]]
| system                          = [[Chicago "L"]]
| status                          = Operating
| locale                          = [[Chicago]], [[Oak Park, Illinois|Oak Park]], [[Forest Park, Illinois|Forest Park]], and [[Rosemont, Illinois|Rosemont]], [[Illinois]]
| start                           = [[O'Hare (CTA station)|O'Hare]]
| end                             = [[Forest Park (CTA station)|Forest Park]]
| stations                        = 33
| routes                          = O'Hare–Forest Park
| daily_ridership                 = 72,475 (avg. weekday 2023)
| open                            = Oldest segment: {{Start date and age|1895|05|06}}<br>Current operation: {{Start date and age|1958|06|22}}
| close                           = 
| owner                           = Chicago Transit Authority
| operator                        = [[Chicago Transit Authority]]
| character                       = Expressway median, subway and [[Elevated railway|elevated]]
| stock                           = Mixed [[2600-series (CTA)|2600-]] and [[3200-series (CTA)|3200-series]], [[5000-series (CTA)|5000-series]] only on rush hour, [[7000-series (CTA)|7000-series]]<br />8-car trains (typical, maximum)
| linelength                      = {{convert|26.93|mi|km|1|abbr=on}}
| tracklength                     = 
| depot                           = [[Desplaines Yard]], [[Rosemont Yard]]
| tracks                          = 
| gauge                           = {{track gauge|ussg|allk=on}}
| electrification                 = {{600 V DC|conductor=third rail}}
| minradius                       = 
| speed                           = 
| elevation                       = 
| map                             = {{switcher
|{{maplink-road|from=Blue Line (CTA).map}}
|Show interactive map
|{{Blue Line (CTA)}}
|Show route diagram map
}}
| map_state                       = 
}}

The '''Blue Line''' is a {{convert|26.93|mi|km |adj=mid|-long}} [[Chicago "L"]] line which runs from [[O'Hare International Airport]] at the far northwest end of the city, through downtown via the [[Milwaukee–Dearborn subway]] and across the [[West Side, Chicago|West Side]] to its southwest end in [[Forest Park, Illinois|Forest Park]], with a total of 33 stations (11 on the Forest Park branch, 9 in the Milwaukee–Dearborn subway and 13 on the O'Hare branch). At about 27 miles, it is the longest line on the Chicago "L" system and second busiest, and one of the longest local subway/elevated lines in the world. It has an average of 72,475 passengers boarding each weekday in 2023.<ref name="cta-report">{{cite web | title=Annual Ridership Report - Calednar Year 2023 | publisher= [[Chicago Transit Authority]]|url=https://www.transitchicago.com/assets/1/6/2023_Annual_Ridership_Report.pdf| date= January 23, 2024| accessdate=November 21, 2024}}</ref>

Chicago's Blue Line and [[Red Line (CTA)|Red Line]] offer 24-hour service, every day, year-round. This makes Chicago, New York City, and Copenhagen the only three cities in the world to offer local nonstop rail service throughout their city limits 24 hours a day, seven days a week. The Blue Line is one of two lines in Chicago with more than one station having the same name, with the [[Green Line (CTA)|Green Line]] being the other. (The Blue Line has two stations at Harlem Avenue: one in the Kennedy Expressway on the Northwest side and one on the Eisenhower Expressway in [[Forest Park, Illinois]]. It also has two stations on Western Avenue: one on the segment between downtown and O'Hare, and one immediately west of downtown.) The Blue Line also has two in-system transfers (both in the Loop), and does not share tracks with any other 'L' line.

Before the adoption of color-coded names, the Blue Line was referred to as the '''West-Northwest''' Route, or more commonly, the '''O'Hare-Congress-Douglas''' route for its three branches. The Congress and Douglas branches were renamed for their terminals, '''Forest Park''' and '''54th/Cermak''', when the current color naming system was adopted in 1993. Blue Line service on the Douglas segment was replaced in April 2008 by the [[Pink Line (CTA)|Pink Line]].<ref name="CTAnews">{{cite web|url=http://www.transitchicago.com/blueline/|title=Blue Line|publisher=[[Chicago Transit Authority]]|location=[[Chicago]]}}</ref>

The Blue Line is one of five "L" lines that run into Chicago suburbs, with the others being the Green, [[Purple Line (CTA)|Purple]], Pink, and [[Yellow Line (CTA)|Yellow]] lines. The Blue Line runs in three suburbs: Rosemont, Oak Park, and Forest Park.