What is a Rotary District and why do we have them?
“A District is a group of Rotary clubs in a geographical area that linked for administrative purposes.  The activities and organization of a Rotary district exist solely to support Rotary Clubs and enhance their efforts.” – quoted from the Manual of Procedure 2013 Version (MOP).
A district is there to assist Rotary Clubs in training leaders, help with membership recruitment, to assist with Rotary Grants both locally and internationally, help them promote their public image and media exposure. Each District has a District Governor, Assistant Governors (the number varies on the size of the district and the District Governor), a District Treasurer, District Secretary and District Historian plus a number of other leaders to aid the clubs in each District anyway that they can.  Districts also have many of the same leaders as a club – Membership Chair, Foundation Chair, Event Chairs, Nominating Committee, Budget Committee, a Newsletter Editor plus in this day and age a Website Administrator and future leaders already lined up to step up during the next three years. 
Rotary International periodically realigns districts to make them more efficient and economical for Rotary International.  Rotary International pulls all incoming District Governors from all over the world together yearly to train them for their position as District Governor just like all Districts pull all incoming presidents-elect from their District together at PETS (Presidents-elect Training Seminar) yearly to train them for their upcoming position as Club President.   District Governors-elect just like presidents-elect cannot take on their position come July 1st if they have not attended this training.
Our District clubs have been in many Districts during their history as a Rotary Club.  The Rotary Club of Portland is our oldest existing Rotary Club and has been in ten Districts.  See the chart below to see how many currently existing District 7780 clubs have been in different districts over the years.  I have not included clubs that have turned in their charters over the years or moved to another district.
District numbers are as follows:
1915-1918 District 1                           Number of existing clubs - 1
1918-1922 District 2                           Number of existing clubs - 3
1922-1924 District 31                         Number of existing clubs - 7
1924-1926 District 8                           Number of existing clubs - 11
1926-1937 District 38                         Number of existing clubs - 11
1937-1949 District 193                       Number of existing clubs - 12
1949-1956 District 285                       Number of existing clubs - 12
1956-1990 District 779                       Number of existing clubs - 30
1990-1991 District 778                       Number of existing clubs - 32
1991-to February 23, 2016 7780         Number of existing clubs - 39