Des Moines vs capital of Iowa

Des Moines

name
  • A city in Washington. 

  • The capital city of Iowa, United States and the county seat of Polk County. 

  • A village in New Mexico. 

  • A river in the United States, that flows from southern Minnesota into the Mississippi. 

capital of Iowa

How often have the words Des Moines and capital of Iowa occurred in a corpus of books? (source: Google Ngram Viewer )