Charles Rattigan, David Roberts, and Andrew Stewart Green Mountain Digital

Twenty years ago, Andrew Stewart, founder of his eponymous nature book publishing house, wanted to put his heavy reference guides onto portable electronic devices so readers wouldn't have to lug them into the field. Such devices—iPhones, Kindles, and the like—had yet to be invented, but that didn't stop Stewart, an avid camper, hiker, and overall outdoors nut, from buying digital rights to thousands of texts, maps, and illustrations. Fast-forward to April 2009: Stewart, who also headed Harry N. Abrams and other renowned publishers, launched Green Mountain Digital to create nature guides for smartphones with his longtime friend, Charles Rattigan, a producer for PBS and National Geographic, and David Roberts, a former Citigroup (C) banking executive. A little more than a year later, the 12-employee company is selling 27 mobile apps focused on North American flora and fauna. Audubon Birds: A Field Guide to North American Birds, which is exactly what it sounds like, is the most popular of Green Mountain Digital's offerings and sells for $20. A close second is A Field Guide to Birds, Mammals, Wildflowers, and Trees, also Audubon, which costs $40. Rattigan, 68, Roberts, 64, and Stewart, 72, say that the company had $120,000 in 2009 revenue, projects $1.5 million in 2010, and has raised $2.35 million from angel investors. They expect Green Mountain Digital to be profitable by mid-2011. Its next two apps—Orvis Fly Fishing: The Ultimate Fly-Fishing Guide and Audubon Butterflies: A Field Guide to North American Butterflies—are each in review at Apple (AAPL) and will go live this August, the founders say.

—Lauren Hatch (posted on August 4, 2010)