Needs Historic Football Photos

Dear Rich: I am a retired NFL Veteran and also a retired Special Educator. I have written a book called "THE FIRST GAME" which is about the evolution of American Football. I need a recommendation for someone who specializes in historic American football photos. 
If you're writing about the first college game (1869) or the first NFL game (1920), keep in mind that all photographs published before 1924 are in the public domain, meaning you are free to use them without anyone's permission. To give you an idea of the breadth of imagery check out the 1,023 historic football photos, prints, and drawings available at the Library of Congress. Other sources of public domain content, for example, the Public Domain Review also contain historic football imagery.
Football photos published after 1923. If the photo you want was published from 1924 through 1963, chances are also good it is free to use if the owner failed to renew it (which 85% of owners failed to do). You can check whether a work was renewed by following the instructions in Circular 22.
If you're seeking photos protected by copyright, you'll need to either (1) deal with a photo researcher/clearance expert, or (2) deal with a photo licensing service. You can find the former by  searching online for "freelance photo researcher" or "photo clearance." As for finding photo licensing services, you're best off checking out AP Images, Icon Sportswire, and Getty (for Sports Illustrated's photo collection).