Notes:

• In 1997, MLB retired Jackie Robinson's number 42 meaning no other player in MLB could ever wear it.  However, it was grandfathered to anyone who was currently wearing the number.  Of course, Mariano Rivera was one of those already sporting #42 so when Mariano's number 42 was retired on September 22, 2013, the number hung alongside all the other retired numbers was changed to the Yankee pinstriped style with matching font.  To honor Robinson, a plaque was placed in Monument Park.
• Mariano Rivera is the only Yankee to appear as an active player while wearing his retired number.
• Six Yankees wore their previously retired numbers in a managerial/coaching role: Billy Martin, Yogi Berra, Mickey Mantle, Whitey Ford, Don Mattingly and Ron Guidry.
• Mariano Rivera and Whitey Ford are the only two Yankees to have their numbers retired while still wearing them in an active role on the team (Mariano was still playing and Whitey was a coach in 1974 when the number was retired.) (Thanks Michael R. from Irvine, CA)
• Of all the numbers that have been retired, only Bill Dickey would later go on to wear a different uniform, #33, as a coach (Thanks again to Michael R.)

*Michael R. from Irvine, CA notes that #9 and #32 were planned for retirement on Saturday, July 21, 1984 (Old-Timer's Day), but rain resulted in a cancellation and the ceremonies were moved to the next day.

**Michael R. from Irvine, CA notes that the 2013 Yankees Media guide states that while Gehrig's number retirement was announced to the public (an on-field announcement by co-owner Ed Barrow) on that famous July 4, 1939 afternoon, the number wasn't "officially" retired until January 6, 1940.  For the purposes of this website, I'll choose to go with the more widely accepted first announcement of July 4, 1939 as the retirement date, but in the interest of completeness, I felt the unusual January 6th "announcement" deserved mention.  Here's a link to an archived article.