After crossing the Lewis & Clark Viaduct, I-70 enters Missouri. This portion is called "The George Brett Super Highway" after the Kansas City Royals Hall of Fame third baseman. It encounters a loop of freeways, called the Alphabet Loop, which contains I-70 as well as I-35, I-670, U.S. 24, U.S. 40, U.S. 71, and U.S. 169. In the southern part of this loop, I-670 cuts directly through the downtown while I-70 bypasses the taller buildings a few blocks north near the Missouri River. Westbound I-670 is also designated Alternate I-70 making this the only permanent "alternate" interstate in the country. Most of the interstates in this loop are in their second mile, so all exits (no matter the which interstate carries the road) are numbered 2 and suffixed with every letter of the alphabet except I, O and Z.
The section of I-70 in Downtown Kansas City is approximately the southern city limits of "City of Kansas" when it was incorporated in 1853. The first two auto bridges in Missouri mark the city's original boundaries with the Broadway Bridge (Kansas City) (U.S. Route 169) being the west boundary while the Heart of America Bridge (Route 9) is the east boundary. Another intersection of note is the second traverse of I-435. This is primarily notable because it immediately precedes the Truman Sports Complex (home of both Arrowhead Stadium and Kauffman Stadium) and also because the entrance ramps from I-435 northbound onto I-70 eastbound also serve as the exit ramps from I-70 into the Truman Sports Complex parking lots. This section of the Interstate is marked as the "George Brett Super Highway", named after the Kansas City Royals third baseman who played the entirety of his career (1977-1993) at "The K". The last interstate intersection in the immediate Kansas City metro area is with I-470 in Independence.
After passing Kansas City, I-70 traverses the length of Missouri, west to east. It passes through the largest city between Kansas City and St. Louis, Columbia, which is about halfway between the two major cities, and the home of the University of Missouri. The terrain is rolling with some hills and bluffs near rivers. I-70 also crosses the Missouri River twice (as did the original US 40)--at Rocheport, about 15 miles west of Columbia, and at St. Charles, about 20 miles northwest of St. Louis. Most of the highway on this stretch is four-lane. Various proposals have been made to widen it (at an estimated cost of $3.5 billion) including turning it into a toll road.[6] I-70 eventually gets into the St. Louis metro area and U.S. Route 40 splits to the south, along with U.S. Route 61, which does not have a concurrency with I-70. The intersecting road will be upgraded to Interstate standards because of the upgrade to Interstate 64.[7] After this interchange, I-70 intersects two child routes, I-270 and I-170. I-70 then heads into the city limits of St. Louis, designated "The Mark McGwire Highway" after the Cardinals former first baseman (1997-2001). It continues south to intersect with I-64, U.S. 40, and I-55, which then become concurrent as they head east to cross the Mississippi River on the Poplar Street Bridge.
The 1985 World Series between the Kansas City Royals and St. Louis Cardinals was nicknamed the "I-70 Series" because St. Louis and Kansas City are the two endpoints of I-70 in Missouri and the highway passed both Busch Stadium and Royals Stadium.