President James A. Garfield (November 19, 1831 - September 19, 1881) and the assassin Charles J. Guiteau

 

Wikipedia entries:

-     https://en.wikipedia.org/wiki/James_A._Garfield

-     https://en.wikipedia.org/wiki/Assassination_of_James_A._Garfield

-     https://en.wikipedia.org/wiki/Charles_J._Guiteau

 

Guiteau's brain

-     The Atlantic: This Is the Brain that Shot President James Garfield (October 4, 2015)
https://www.theatlantic.com/politics/archive/2015/10/this-is-the-brain-that-shot-president-james-garfield/454212/

-     Mental Floss: This Is the Brain of the Man Who Shot James A. Garfield (July 2, 2015; updated June 18, 2019)
http://mentalfloss.com/article/65828/brain-man-who-shot-james-garfield

 

"Murder of a President": PBS American Experience episode aired February 2, 2016

-     PBS site (includes transcript, clips, other features)
https://www.pbs.org/wgbh/americanexperience/films/garfield/

-     complete film on Amazon Prime
https://www.amazon.com/American-Experience-President-Michael-Murphy/dp/B01BCU1QYK

 

Candice Millard's book Destiny Of The Republic

-     "Candice Millard leaves us feeling that Garfield's assassination deprived the nation not only of a remarkably humble and intellectually gifted man but one who perhaps bore the seeds of greatness." - The Wall Street Journal

-     book site with excerpt: http://www.candicemillard.com/destiny-of-the-republic.html

-     reviews with interesting commentary:
https://www.nytimes.com/2011/09/12/books/destiny-of-the-republic-on-garfield-by-candice-millard-review.html
https://www.nytimes.com/2011/10/02/books/review/destiny-of-the-republic-by-candice-millard-book-review.html

-     Wikipedia entry about the book:
https://en.wikipedia.org/wiki/Destiny_of_the_Republic

 

Garfield's proof of the Pythagorean Theorem

-     Gizmodo (August 6, 2013): James Garfield Was the Only U.S. President to Prove a Math Theorem
https://io9.gizmodo.com/james-garfield-was-the-only-u-s-president-to-prove-a-m-1037750658

-     Garfield's Proof of the Pythagorean Theorem as published on page 161 of the New England Journal of Education, April 1, 1876, along with additional explanatory text and images (in Convergence, an online journal of the Mathematics Association of America)
https://www.maa.org/press/periodicals/convergence/mathematical-treasure-james-a-garfields-proof-of-the-pythagorean-theorem