The preservation of fruit in alcohol is a traditional method found in many European cultures. The 1881 edition of the Fanny Farmer cookbook contains recipes for both "brandied cherries" and "brandied peaches". Maraschino cherries originated in Dalmatia as a means of preserving the local Marasca sour cherry in Maraschino liquor, which is itself made from the Marasca cherry.
By the 1880s, these preserved cherries had reached as far as Paris, where they became a fashion among the cafés and adorned drinks and pastries. Within the decade, the "maraschino cherry" had appeared in the finer restaurants of New York City.
Demand was such that American cherry producers and confectioners began to work towards duplicating the expensive import. The Royal Anne sweet cherry and brandy were the primary ingredients, along with sugar and almond oil (to help approximate the taste of the maraschino liquor itself). When Prohibition went into effect, banning the import of the authentic Italian alcohol-preserved cherry, the domestic producers suddenly had the market to themselves. So they made the cherries sweeter; they had to in order to extend the shelf life, just as with jams and jellies. After the repeal of the Prohibition, the maraschino cherry was a dessert food, adorning piles of ice cream and slices of pineapple upside-down cake, but too sweet for use in the bar.
The modern maraschino cherry is a large sweet cherry that is picked while still green. Much like the process that produces olives, it is pitted and soaked in a brine solution that includes sulfur dioxide and calcium chloride. This draws the green color from the cherries as it preserves them. The blanched unripe fruit is then soaked in a syrup of natural and artificial sweeteners, colors, and flavorings. The color of the maraschino cherry is a garish bright red, although during the holiday season lurid green maraschinos can be spotted on the supermarket shelves. (Zerotime notes that fluorescent yellow ones are available in the Antipodes.) This modern maraschino cherry is most ideal for garnishing a fountain soda in order to give a child a drink "just like the grown ups'".
However, there are several mixed drinks that demand a cherry as garnish. If cherries are in season, pit some and macerate them in a mixture of kirschwasser and amaretto for a few hours. But even if all you have at hand is a jar of the lurid maraschinos, they can be improved by draining, rinsing, and setting them in a mixture of vodka, kirschwasser, and amaretto to macerate overnight.
Many many thanks to the awesome factgirl who was instrumental to the production of this node, allowing me access to the contents of her research library and helping to investigate pictorial evidence of maraschino cherries in Impressionist paintings, which, alas, came to naught. (It turns out that the bottles with the red sploch on their labels in Eduard Manet's A Bar at the Folies-Bergeres are Bass Ale, the red sploch is the first registered trademark in Britain.)
The beautiful but frigid icicle mentioned to me that the maraschino cherry is the official fruit of Oregon State University. When she first said this to me, deep in our cups, we had a maraschino cherry apiece, but subsequent perusal of the OSU course catalog discovered a required course in the College of Agricultural Sciences FST 102, described as "The interdisciplinary nature of food science and technology is demonstrated by examining historical, technological, and scientific aspects of maraschino cherry production". As it turns out, the modern American maraschino cherry (perish the thought) was developed at OSU. For a brief period in the 1930s, their football team took to the field led by their mascot, the Oregon Maraschino.