What is the criteria for inclusion in the list? I ask because of interesting omissions, such as Ottawa, capital of Canada, population over 1M; Fredericton, capi

What is the criteria for inclusion in the list? I ask because of interesting omissions, such as Ottawa, capital of Canada, population over 1M; Fredericton, capital of NB (NB's most populous city is included, but not the capital).... Just curious.