The Chicago, Rock Island and Pacific Railroad (CRI&P), commonly known as the Rock Island Line or simply The Rock, was a prominent historic American Class I railroad that operated extensively in the Midwest and Western United States from the mid-19th century until its bankruptcy and cessation of operations in 1980. Its origins date back to the Rock Island and LaSalle Rail Road Company, chartered in Illinois on February 27, 1847, which aimed to connect Chicago to Rock Island. The railroad expanded through key mergers, including the acquisition of the Mississippi and Missouri Railroad (M&M) by the Chicago and Rock Island Railroad on July 9, 1866, formally establishing the Chicago, Rock Island and Pacific Railroad Company. This consolidation allowed the line to extend westward toward the Pacific, serving vital routes for freight and passengers across states like Illinois, Iowa, Missouri, Kansas, Oklahoma, and Arkansas. At its peak, the Rock Island network spanned over 7,000 miles, playing a crucial role in agricultural transport, industrial development, and westward expansion.

Throughout its history, the railroad underwent several reorganizations and leadership changes to navigate financial challenges and competition from rivals like the Union Pacific and Atchison, Topeka and Santa Fe. Notable figures included Ransom Reed Cable, who joined as a director in 1877 and became president in 1883, steering the company until his retirement in 1902. The Rock Island faced ongoing economic pressures, including the Great Depression, post-World War II shifts in transportation, and labor strikes. By the 1970s, mounting debts and operational inefficiencies led to bankruptcy filings in 1975, with full cessation of operations in 1980. Following liquidation, significant portions of its tracks and assets were acquired by other railroads, including interests controlled by Philip Anschutz, who purchased key lines in the 1980s.

The Rock Island's legacy endures in the regional economies it helped build and in preserved historical artifacts, such as museums and short-line operators using former routes. Its story exemplifies the boom-and-bust cycles of America's rail industry, marked by innovation in the 19th century and decline amid regulatory and market changes in the 20th century.