Both teams play in League One
This time last season, MK Dons were 16th in The Championship. AFC Wimbledon were in League Two in 12th place on the same date.
There were exactly 45 places in the English league pyramid a year ago between the two teams. On Sunday afternoon, AFC Wimbledon overtook their rivals for the the first time ever.
AFC Wimbledon were 3-1 winners away to Oxford United. At the same time MK Dons lost 1-0 to Port Vale. That leapfrogged Neal Ardley's team over last season's Championship side.
On May 30th, 2002, AFC Wimbledon were founded. The club were created on the back of Wimbledon FC leaving London and being moved to Milton Keynes. That team eventually became MK Dons.
Until this season, the two teams never played in the same division. AFC Wimbledon were only promoted to the Football League in 2011-12 and were promoted last season to League One through the play-offs. They have risen seven divisions since 2002-03, after beginning in the Combined Counties League Premier Division.
After re-branding from Wimbledon FC to MK Dons, the team began their existence in League One, and spent spells in both League Two and The Championship.
The two teams have played each other three times, but have yet to meet in the League. That opening game will come next month. The FA Cup, League Cup and Football League Trophy have all hosted games between the two teams with the Dons having a 2-1 overall record.
It's been a historic weekend for AFC Wimbledon fans.