The Rock Island District (RI) is a Metra commuter rail line from Chicago, Illinois, southwest to Joliet. Metra does not refer to its lines by color, but the timetable accents for the Rock Island District line are "Rocket Red" in honor of the Chicago, Rock Island and Pacific Railroad's Rocket passenger trains.

The Suburban Line was built in 1870 as a steam dummy line, splitting from the main line just north of 99th Street, running west along 99th and turning south to the present line at the S-curve just south of 99th. The crossing of the Pittsburgh, Cincinnati, Chicago and St. Louis Railway midway along 99th was known as Dummy Crossing. In the early 1890s the line was extended north to 89th Street in conjunction with the expansion of the Chicago Terminal Transfer Railroad, and the portion on 99th was removed.

The track is owned by Metra, bought from the bankrupt Chicago, Rock Island and Pacific Railroad for $35 million in December 1982 (equivalent to $111 million in 2023). The Regional Transportation Authority had signed a contract with the Rock Island in 1976 to fund service, and in 1980 the Chicago and North Western Railway began operating the Rock Island District (the Rock Island also ceased operations that year.) In spring 1981 the C&NW stepped away, and the Northeast Illinois Regional Commuter Railroad Corporation (Metra) was formed to take over operations. Through freight trains on the line are operated by CSX and Iowa Interstate Railroad on a trackage rights agreement. In addition, Chicago Rail Link has rights to operate local freight service on the whole district, and it also uses the line between Gresham Wye and Blue Island to connect with the Iowa Interstate and Indiana Harbor Belt Railroads.

A new station at 35th Street and Federal Street opened on April 3, 2011 to serve U.S. Cellular Field and the Illinois Institute of Technology. It was named 35th Street/'Lou' Jones/Bronzeville Station after Lovana Jones who was an Illinois State Representative in the Bronzeville neighborhood.

The Englewood Flyover, an overpass located in the Chicago neighborhood of Englewood, eliminated delays for the Rock Island. The overpass replaced a diamond crossing with the Norfolk Southern's Chicago Line. The overpass proposed by Chicago Region Environmental and Transportation Efficiency Program (CREATE), which cost $142 million to construct, was completed in October 2014.

In recent years, Metra has expressed a desire to electrify and modernize the line if funding became available. In October of 2023, Metra announced the order of 16 lightweight Stadler FLIRT Akku electric multiple unit trainsets that would likely be used on the Beverly Branch. They could be used to increase frequency and speed.

As of September 7, 2021, Metra operates 80 trains (40 inbound and 40 outbound) on the Rock Island District on weekdays, with 21 trains providing roundtrip service to and from Joliet, three to and from Tinley Park - 80th Avenue, and 16 to and from Blue Island-Vermont Street. Between Gresham and Blue Island, all trains terminating at Blue Island as well as four evening through-trains to and from Joliet operate via the suburban branch, while all other trains remain on the mainline.

On Saturdays, Metra operates 33 trains (16 inbound and 17 outbound) on the line, with 10 roundtrips to and from Joliet, six roundtrips to and from Blue Island, and an additional outbound train to Joliet. The Blue Island short-turn trains, as well as four inbound and five outbound through-trains to and from Joliet operate over the suburban branch, while the other six Joliet through-trains in each direction remain on the mainline.

On Sundays, Metra operates 28 trains (14 roundtrips), eight to and from Joliet, and six to and from Blue Island. All six Blue Island short-turn trains as well as two through-trains to and from Joliet operate over the suburban branch, while the other six Joliet through-trains in each direction remain on the mainline.

In June 2015, Metra began weekend express service on the Rock Island District. The six express trains that operate on both Saturday and Sunday run express from 35th Street to Blue Island-Vermont Street via the main line before making all stops to Joliet, bypassing the suburban branch entirely. Local trains run as well, making all stops on the suburban branch and terminating at Blue Island-Vermont Street. This cuts about 20 minutes off the trips from Blue Island to downtown. On August 23, 2015, Metra announced that the weekend express service would become permanent upon completion of the trial period on November 29, 2015.

The Rock Island District runs a few empty equipment move (deadhead) trains, most during weekdays. Inbound deadheads are scheduled between the Joliet, Mokena-Front Street, and Tinley Park stations and run to Blue Island-Vermont Street.

There have been proposals to extend the line from Joliet to LaSalle-Peru in LaSalle County with intermediate stations at Rockdale, Minooka, Morris, Seneca, Marseilles, Ottawa, and several other towns. A feasibility study was completed in 2003. As of 2022, an extension only as far as Minooka has been considered feasible in the near future, and there are no currently active plans to carry out the extension.

After the passage of the Rebuild Illinois, $20 million was allocated for the long planned construction of a new Auburn Park station. Construction is expected to start in 2020.

In the beginning of 2021, fares on the Rock Island, as well as the Metra Electric District, were cut in half for all passengers as part of a pilot program.

From 2014-2019 annual ridership declined from 8,544,753 to 7,338,133, an overall decline of 14.1%. Due to the COVID-19 pandemic, ridership dropped to 1,952,547 passengers in 2020 and 1,669,273 passengers in 2021.

County	Zone	Location	Station	Connections and notes
Cook	1	Chicago	LaSalle Street	Chicago "L": Blue (at LaSalle), Brown Orange Pink Purple (at LaSalle/Van Buren) CTA Bus: 1, 7, 22, 24, 36, 126, 130, 151, 156 City of Valparaiso: ChicaGo Dash
	2		35th Street	Chicago "L": Red (at Sox–35th), Green (at 35th–Bronzeville–IIT) CTA Bus: 24, 31, 35, 39
			Englewood	Closed late 1970s
			Normal Park	Closed
			Hamilton Park	Closed
			Auburn Park	Closed 1978, to reopen in 2025
	2		Gresham	CTA Bus: 8A, 24, 87, N87
			Beverly branch begins
			95th Street–Longwood (rush only)	CTA Bus: N9, 95, 112 Pace: 381, 395
			99th Street–Longwood	Closed 1985
			103rd Street–Washington Heights (rush only)	CTA Bus: 9, 103, 112
			Givins	Closed 1984
		Blue Island	Blue Island–Vermont Street	Metra: ■ Metra Electric (at Blue Island) Pace: 348, 349, 359, 385
			Beverly branch ends
		Robbins	Robbins	Pace: 359
		Midlothian	Midlothian	Pace: 354
	3	Oak Forest	Oak Forest	Pace: 354, 364, 383
		Tinley Park	Tinley Park	Pace: 386
	4		Tinley Park–80th Avenue
		Mokena	Hickory Creek
Will			Mokena
		New Lenox	New Lenox
		Joliet	Joliet	Metra: ■ Heritage Corridor Amtrak: Lincoln Service, Texas Eagle Pace: 501, 504, 505, 507, 508, 509, 511, 832, 834

The entire branch is in Cook County, Illinois.

Zone	Location	Station	Connections and notes
2	Chicago	Brainerd	CTA Bus: 9 Ashland
		91st Street–Beverly Hills
		95th Street–Beverly Hills	CTA Bus: 95 Pace: 381, 395
		99th Street–Beverly Hills
		103rd Street–Beverly Hills	CTA Bus: 103
		107th Street–Beverly Hills
		111th Street–Morgan Park	CTA Bus: 112
		115th Street–Morgan Park
	Blue Island	119th Street	CTA Bus: 119
		123rd Street
		Prairie Street
		Blue Island–Vermont Street	Metra: ■ Metra Electric (at Blue Island) Pace: 348, 349, 359, 385

• Beverly/Morgan Railroad District

• J. David Ingles, Metra: "Best Commuter Train", Trains July 1993

• Official website