I really like maps, and several weeks ago I posted a figure that illustrates the spread of world religions over history. One of the themes of that figure is the relatively late expansion of Christianity throughout the world–mainly in the last several hundred years.
Here’s a map by sociologist Robert Woodberry, at the University of Texas, that pinpoints Protestant mission stations throughout the world in 1925. (His website has the same map for other years as well). They are concentrated in South America, Sub-Saharan Africa, India, Eastern China, and Japan. Clearly they were more successful in some areas than others, but this map illustrates the wide influence of these missionaries.