Chicago (Zbigniew Bzdak / July 1, 2011)

1942: Butch O'Hare flies mission that won him Medal of Honor. (Airport renamed O'Hare in 1949.)

1942: The Atomic Age begins at the University of Chicago with first controlled nuclear chain reaction.

1943: Deep-dish pizza mecca Pizzeria Uno opens.

1943: All-American Girls Baseball League founded by Cubs owner P.K. Wrigley.

1944: Germany's U-505 submarine captured — later to become major exhibit at Museum of Science and Industry.

1945: Cubs' last trip to World Series, where they lost to Detroit.

1945: Chicago Transit Authority is established.

1945: Ebony magazine launched.

1946: University of Illinois starts holding classes at Navy Pier.

1947: First parking meters installed in Chicago.

1948: Launch of Chicago Sun-Times and WGN-TV.

1949: Municipal Airport renamed Midway; Orchard Field renamed O'Hare.

1950: Chicago population peaks at 3,620,962.

1950: Chess Records founded.

1951: Edens Expressway (first in Chicago) opens.

1952: Chicago American Giants, Negro Leagues team, disbands.

1953: First issue of Playboy magazine is produced in Hugh Hefner's Hyde Park apartment.

1954: Lyric Opera founded.

1955: Richard J. Daley elected mayor for the first time.

1955: Congress Expressway opens (later renamed Eisenhower Expressway).