The Midwestern United States (in the U.S. generally referred to as the Midwest) is one of the four geographic regions within the United States of America that are officially recognized by the United States Census Bureau, says Wikipedia.
The region consists of twelve states in the central and inland northeastern US: Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin.
Yes. You see that there's a discrepancy between the Census Bureau and this map. That's a traditional if minor controversy.