It was originally formed by the United States Census Bureau in 1950 and consisted of the Kentucky county of Jefferson and the Indiana counties of Clark and Floyd. As surrounding counties saw an increase in their population densities and the number of their residents employed within Jefferson County, they met Census criteria to be added to the MSA. Jefferson County, Kentucky (contiguous with Louisville Metro), plus twelve outlying counties — eight in Kentucky and four in Southern Indiana are now a part of this MSA.

• Populations are based upon published estimates by the United States Bureau of the Census.

¹County was not a part of Louisville, KY-IN MSA at the time of this Census and the county's population is not included in MSA total.

²Census defined area did not exist during this Census. Population totals are for counties included in 2000 Census MSA or CSA estimates. Population is shown for comparison purposes only and should not be used as a reference.