Question: Into what company did the railroad which had operated the Twin Cities Zephyr merge in 1970?
Context: The Twin Cities Hiawatha, often just Hiawatha, was a named passenger train operated by the Chicago, Milwaukee, St. Paul and Pacific Railroad (also known as the Milwaukee Road), and traveled from Chicago to the Twin Cities.  The original train takes its name from the epic poem "The Song of Hiawatha" by Henry Wadsworth Longfellow.  There are a number of Hiawatha-themed names within the city of Minneapolis, the terminus of the original train.  The first "Hiawatha" ran in 1935; in 1939 the Milwaukee Road introduced a second daily trip between Chicago and Minneapolis.  The two trains were known as the Morning Hiawatha and Afternoon Hiawatha, or sometimes the "AM Twin Cities Hiawatha" and "PM Twin Cities Hiawatha".  The Milwaukee Road discontinued the "Afternoon Hiawatha" in 1970 while the "Morning Hiawatha" continued running until the formation of Amtrak in 1971. The Nebraska Zephyr was a streamlined passenger train operated by the Chicago, Burlington and Quincy Railroad (CB&Q, commonly known by the shorter name of "Burlington") between Chicago, Illinois, Omaha, Nebraska and Lincoln, Nebraska.  It operated from 1947 to 1971.  Until 1968 the two original "Twin Cities Zephyr" articulated trainsets, the "Train of the Gods" and "Train of the Goddesses", operated the service and became synonymous with it.  The "Nebraska Zephyr" was one of many trains discontinued when Amtrak began operations in 1971.  The "Train of the Goddess" set is preserved at the Illinois Railway Museum in Union, Illinois. The Chicago, Burlington and Quincy Railroad (reporting mark CBQ) was a railroad that operated in the Midwestern United States.  Commonly referred to as the Burlington or as the Q, the Burlington Route served a large area, including extensive trackage in the states of Colorado, Illinois, Iowa, Kansas, Kentucky, Missouri, Montana, Nebraska, Wisconsin, Wyoming, and also in New Mexico and Texas through subsidiaries Colorado and Southern Railway, Fort Worth and Denver Railway, and Burlington-Rock Island Railroad.  Its primary connections included Chicago, Minneapolis-St.  Paul, St. Louis, Kansas City and Denver.  Because of this extensive trackage in the midwest and mountain states, the railroad used the advertising slogans "Everywhere West", "Way of the "Zephyrs"", and "The Way West".  It merged into Burlington Northern in 1970. A Zephyrette was a hostess on the "California Zephyr" between 1949 and 1970, while the train was jointly operated by the Chicago, Burlington and Quincy Railroad, the Denver and Rio Grande Western Railroad, and the Western Pacific Railroad.  The position was the brainchild of Velma McPeek, the Burlington's Supervisor of Passenger Train Services, and was part of an effort to attract families to rail travel and accommodate their needs.  Zephyrettes first appeared on the "Denver Zephyr" in 1936, and shortly thereafter on the "Twin Cities Zephyr", but the position was discontinued during World War II.  Zephyrettes resumed service after the war in 1949, but only on the "California Zephyr". The Ak-Sar-Ben Zephyr was a streamlined passenger train operated by the Chicago, Burlington and Quincy Railroad (CB&Q) between Lincoln, Nebraska and Chicago, Illinois, United States.  The first version operated from 1940 to 1947; a revived service operated from 1953 to 1970.  The "Ak-Sar-Ben" portion of name was created by spelling Nebraska (Neb-ras-ka) backwards and taken from a fraternal organization of the same name.  "Zephyr" was a name applied by the CB&Q to many of its trains, beginning with the "Pioneer Zephyr" in 1934.  The name derived from "Zephyrus", the Greek god of the west wind. The Zephyr Rocket was an overnight passenger train operated jointly by the Chicago, Burlington and Quincy Railroad ("Burlington Route") and the Chicago, Rock Island and Pacific Railroad ("Rock Island Lines") between Saint Louis, Missouri and the Twin Cities of Saint Paul and Minneapolis, Minnesota, with major intermediate stops in Burlington, Cedar Rapids, and Waterloo, Iowa.  The Chicago, Burlington & Quincy carried the train between St. Louis and Burlington, while the Chicago, Rock Island and Pacific carried it between Burlington and Minneapolis/St.  Paul.  Motive power and equipment were pooled and traveled the entire distance without change. The Denver Zephyr was a streamlined passenger train operated by the Chicago, Burlington and Quincy Railroad between Chicago, Illinois, and Denver, Colorado.  It operated from 1936 to 1973.  The "Denver Zephyr" continued operating after the Burlington Northern Railroad merger in 1970.  BN conveyed the train to Amtrak in 1971; Amtrak would merge it with the Chicago–Oakland "San Francisco Zephyr" and drop the name in 1973. The Ozark State Zephyr was a streamlined passenger train operated by the Chicago, Burlington and Quincy Railroad (CB&Q) and the Alton Railroad (the "Alton") between St. Louis and Kansas City in Missouri, home of the Ozarks.  It operated from 1936 to 1939.  The "Zephyr" was one of several short-haul Midwestern routes operated by the CB&Q's then-revolutionary articulated streamlined trainsets, including one of the original "Twin Cities Zephyrs". The Twin Cities Zephyr was a streamlined passenger train on the Chicago, Burlington and Quincy Railroad (CB&Q), running between Chicago and the Twin Cities of Minneapolis and Saint Paul in Minnesota.  It was the second "Zephyr" service introduced by CB&Q after the record-setting Denver–Chicago "dawn to dusk dash" of the "Pioneer Zephyr" trainset. Jodi Livon is an author and psychic medium working primarily in the Twin Cities area.  She is the president of The Intuitive Coach LLC.  Since August 2009, she has been the Resident Psychic on KSTP-TV ABC "Twin Cities Live".  On March 25, 2011 Livon read supermodel Cheryl Tiegs on "Twin Cities Live.”  In another notable segment on “Twin Cities Live,” Jodi and Dave Schrader, explored First Avenue (nightclub) in Minneapolis to see if it’s haunted.  Livon has also been featured on local news station KARE 11.
Answer: Burlington Northern