Many cooks and bakers in Florida claim their recipe is the only authentic version. Be that as it may, the filling is rarely disputed: rather, most debates revolve around the crust and topping. Everyone does agree, however, that green food coloring is for amateurs, and a proper version should be pale yellow. Key limes (also called Mexican or West Indian limes) are the most common lime found throughout the world; the U.S. is the exception in preferring the larger Persian lime.
The two contentious versions center around crust and topping. Early pies probably didn’t even have a crust, but now locals vacillate between traditional pie crust and graham cracker. And then there is the topping. The two camps argue meringue vs. whipped cream. (Apparently these folks have a lot of time on their hands.) Contrary to popular belief, what makes the filling creamy is not cream at all but sweetened condensed milk which is thicker than evaporated milk and comes in a can, first introduced by the Borden Dairy company in the late 1800s. It’s possible that if the sponge divers had anything to do with the pie, they indeed had plenty of canned milk, eggs and Key limes on board (and plenty of sponges for clean-up).
In other countries where Key limes grow, they are used more commonly in many dishes and as a popular flavoring. Although grown for centuries in Asian and South America, they didn’t make an appearance in the U.S. until the late 1800s. which means foodie president Thomas Jefferson missed out entirely. (How he would have loved those pies!)
If you visit Key West, pie factories and bakeries abound, and you can literally eat your way from one end to the other, reveling in the different offerings and deciding for yourself which one you like best. There are also shops which sell dozens of products enhanced with Key lime, such as moisturizers, potpourri, candles, soaps, candies and cookies. Unfortunately for much of America, procuring authentic Key limes is not always easy, and using regular limes just won’t do. Oh sure, you can buy bottled juice which the locals would frown on, but for some it’s better than nothing.