Who said "United we stand, divided we fall"?
That quote can be found on the official seal of Kentucky, which was codified in 1792. It is believed that Governor Isaac Shelby adapted it from a line in "The Liberty Song," written in 1768 by John Dickinson. Here's the relevant excerpt:
Then join hand in hand, brave Americans all, By uniting we stand, by dividing we fall; In so righteous a cause let us hope to succeed, For heaven approves of each generous deed.
A later song, George Pope Morris's "The Flag of Our Union," uses the adapted line.
A song for our banner! The watchword recall Which gave the Republic her station: United we stand, divided we fall! It made and preserves us a nation!
(It should be noted that Morris was born in 1802, so his song clearly came after Kentucky adopted the motto.)