Subsonic Radio

I am in the middle of reading The Hand Behind the Mouse : An Intimate Biography of Ub Iwerks and it goes into detail about the creation of Mickey. In the book it describes Walt telling Ub to start penning new characters, and Ub creates Mickey. This was after they were swindled out of the rights to Oswald the Lucky Rabbit. From what I recall, there appears to be conflicting information. In Walt Disney: An American Orginal they describe Walt designing Mickey on a train back from New York.

Does anyone know which is correct? Or if I am remembering incorrectly from the Disney book?

According to the One Man's Dream film that they show at DHS, Walt first drew Mickey on the train from NY like you read in the book. I have not heard the thought that Ub was the first to create Mickey.

im pretty sure disney created him, but ub iwerks did go a long way towards early character development.