What is the population of Osage County?

That depends entirely on which Osage County you are requesting information about. There are three Osage Counties in various states across the US. According to census.gov, the 2007 estimated total population of each of these Osage Counties and which state they are located in are listed alphabetically as follows:

# Osage County, Kansas: 16,459 # Osage County, Missouri: 13,393 # Osage County, Oklahoma: 45,523