From Ye Olde Tavern established in 1760 and still in existence in Brookfield, Mass. George Washington was a guest in 1789 and President John Adams was a guest in 1799.

And the inventor of this great drink of summer? Joe Rickey - Imbibe Magazine has the lowdown on "The Man Behind The Gin Rickey"
And here's their recipe:
2 oz. London dry style gin
Juice of half a lime
Soda water
Glass: Tall
Llime twist or wedge
Combine gin and lime juice in an ice-filled glass, fill with soda water and mix.