it is declared by who wins it
the closets finish in the iditarod was in 1961, when two sleders where 2 seconds apart.
6 dogs at the finish
1978
The largest number of mushers to finish a race is 77.
Bribes the official
Javier Lopez :)
Norman Vaughan
It starts in Willow And Finishes In Nome.
Isaac Okleasik was the musher who won the Iditarod in 1967. That was the first official race.
8 months
The Burled Arch
Current maps on the Iditarod's official website claim 1112 miles, but that includes the cerimonial start in Anchorage that is not timed.