No matter how they identify the other 364 days of the year, on March 17, everyone within the city limits of Chicago considers himself Chirish.As I followed the shuffling crowd toward the green river, I attempted to avoid getting trampled amid the low-toned shouts from drunken teenagers and leering 40-something couples. I stopped in a clothing shop, to be greeted by a police officer singing “Danny Boy” with a surprisingly smooth vibrato voice. “Ah, welcome! We are all Irish today,” he said.As a native Chicago suburbanite who identifies as a Chicagoan on days like March 17, I say there’s nothing...