The route was designated in 1921 as part of the Centennial Road Law , which created a highway system for the state of Missouri . It started at the Arkansas state line and traveled east to Caruthersville , providing a route to St. Louis via Kennett and Poplar Bluff from Pemiscot County . A section from the Dunklin – Pemiscot county line to Hayti was being paved partially in concrete later that year , and did not finish until the next year . The route in Pemiscot County was completed by 1925 , excluding the bridges over Little River , which were completed in 1926 , providing the first all-year crossing over the river . By 1927 , the route was the most heavily used highway in southeast Missouri . The road was flooded during the Great Mississippi Flood of 1927 in April , from the Arkansas state line to Kennett . The waters receded about three months later , and the cost to repair the damage was $ 10,000 ( 1928 USD ) . The last unpaved section from Hayti to Caruthersville began paving in 1930 . Two bridges were being constructed in 1931 , and opened the year after . All of the route was paved by 1932 . The route was widened to two lanes from Kennett to Hayti in 1934 . In 1957 , a bypass around Caruthersville was being built to relieve traffic going through downtown . Known as Fair Boulevard ( due to its vicinity to the American Legion Fairground ) , Route 84 was rerouted to the new bypass as it was state maintained . The boulevard opened in the same year , improving traffic in the area . Markings were installed two years later . The five bridges over the Little River were replaced starting in 1965 , at a cost of $ 802,442 ( 1965 USD ) . In 1969 , an interchange at I-55 was being constructed , and it was completed by 1971 . Route 84 was extended southwards to a new interchange at I-155 by 1977 , replacing a section of Route Y . In November 1980 , US 412 was designated with the route concurrent with Route 84 from Kennett to Hayti . By 2001 , a connector was built from Route 84 and US 412 to I-55 and I-155 . Part of Route 84 and US 412 in Pemiscot County east of Route A to Hayti Heights was expanded to a multi-lane highway by 2004 , and from Kennett to east of Route A by 2010
Great Mississippi Flood of 1927
Great Mississippi Flood of 1927
Missouri Route 84