The explanation is that you basically defined the Eastern Midwest as Ohio + Detroit, with everything else being the Western Midwest.
If you drew a line from Denver, CO to a point south of Buffalo, the midway point would be in Northeast Missouri. Basically the "Eastern" Midwest would be everything east of a line that runs through Duluth, MN while the "Western" Midwest would be everything west of that line. That would put the dividing point as roughly being the "Great Lakes" States of Michigan, Ohio, Indiana, Illinois, and Wisconsin as well as Eastern Pennsylvania and New York, and the "Great Plains" States of Minnesota, North Dakota, South Dakota, Iowa, Kansas, Nebraska, and Missouri and arguably the stretch of Colorado between the Kansas border and Denver.
If you use the "Duluth" line as the border than all of the cities you listed except Minneapolis are part of the Eastern Midwest. If you use the state lines as the border then you move St. Louis to the west.
If you drew a line from Denver, CO to a point south of Buffalo, the midway point would be in Northeast Missouri. Basically the "Eastern" Midwest would be everything east of a line that runs through Duluth, MN while the "Western" Midwest would be everything west of that line. That would put the dividing point as roughly being the "Great Lakes" States of Michigan, Ohio, Indiana, Illinois, and Wisconsin as well as Eastern Pennsylvania and New York, and the "Great Plains" States of Minnesota, North Dakota, South Dakota, Iowa, Kansas, Nebraska, and Missouri and arguably the stretch of Colorado between the Kansas border and Denver.
If you use the "Duluth" line as the border than all of the cities you listed except Minneapolis are part of the Eastern Midwest. If you use the state lines as the border then you move St. Louis to the west.