Established in 1865 under the name Union Pacific Railroad (UP), Southern Branch, it came to serve an extensive rail network in Texas, Oklahoma, Kansas, and Missouri.

In the 1890s, the MKT was commonly referred to as "the K-T", because for a time it was the Kansas–Texas division of the Missouri Pacific Railroad and "KT" was its abbreviation in timetables as well as its stock exchange symbol.

Former Rock Island trackage rights acquired by the Katy also gave it access to Lincoln and Omaha, Nebraska and Council Bluffs, Iowa.

In the late 1890s, a subsidiary once called the Missouri-Kansas-Eastern railroad was established to run from existing MKT rails approaching Kansas City into St Louis via the Missouri River basin.

Congress had passed acts promising land grants to the first railroad to reach the Kansas border via the Neosho Valley.

The Katy portion of the former UP Southern Branch, which had begun building from Fort Riley just north of Junction City, Kansas, was in a heated competition for the prize.

Ragtime composer and pianist Scott Joplin, who was performing in the area at the time, commemorated the event in his piano piece, "The Great Crush Collision March" (which he dedicated to the Missouri-Kansas-Texas Railway).

It sported rail cars with names including Sam Houston, Stephen F. Austin, David Crockett, and James Bowie after prominent men of the state.

[citation needed] On December 1, 1989, the Katy was merged into the MoPac, which is now part of the Union Pacific Railroad system.

The Katy operated these named passenger trains: (On its main line routes, trains originated in St. Louis or in Kansas City, linking in Parsons, KS, split in Denison, TX, with sections going via either through Dallas or Fort Worth, linking again in Waco, then heading south to either San Antonio or Houston.