Casper vs Natrona County

Casper

name

  • A city, the county seat of Natrona County, Wyoming, United States 

  • A male given name from Old Persian, of occasional usage, variant of Caspar. 

  • A mountain in Wyoming 

noun

  • A white person. 

Natrona County

name

  • One of 23 counties in Wyoming, United States. County seat: Casper. 

How often have the words Casper and Natrona County occurred in a corpus of books? (source: Google Ngram Viewer )