Biggest North American "O" Cities by Picture

These are the biggest cities in North America starting with the letter O. Try to guess them. As additional hints, the flag of each city's country and the cities' population figures are given. Some cities have several names or name forms. Here, the Jetpunk standard for spelling the city names has been used as far as possible. Otherwise, this quiz follows the way Wikipedia writes the names in article headlines. In some cases, alternative names are given in parentheses.