Henry Ramos invented the Original Gin Fizz in New Orleans, at his Meyers Restaurant in the 1880’s.  The recipe below was given by Mr. Ramos in 1923.

Ramos Original New Orleans Gin Fizz

One tablespoon powdered sugar
Three or four drops of orange flower water
One half lime (juice)
One half lemon (juice)
One jigger of Old Tom Gin (Old Gordon may be used, but a sweet gin is preferable)
The white of one egg
One half glass of crushed ice
About two tablespoons of rich milk or cream
A little seltzer water (about an ounce) to make it pungent

Together, well shaken and strained

SOURCE:  Thanks to Bob Moulin for sharing a copy of an article from The New Orleans Item-Tribune, August 23, 1925,  containing an interview with Mr. Ramos, along with the recipe for his famous Original Gin Fizz!