Colonel Townsend Whelen, noted hunter and outdoor writer, designed a tent he called the “hunter’s lean-to” in 1925. David Abercrombie ( of the old Abercrombie & fitch fame) manufactured the style and marketed it as the “Whelen Lean-to”. It has been called the Whelen ever since, Colonel Whelen, as a devout minimalist, hardly believed in tents for shelter at all. He wished to be as close to his natural surroundings as was possible and practical. The Colonel considered this design, which almost has the appearance of half a tent, more than adequate for anything short of -20 degrees or severe bugs. With a sloped rear roof, slanted and splayed sides and a short fore roof panel, this tent is a relatively dedicated specialized tarp. Light and easy to pack.
If you want to read a little bit more about the Whelen Lean-To, which I'm sure you don't, start on page 80 of Bradford Angier's Basic Wilderness Survivial Skills. And don't forget to check out Conway, New Hampshire's Tentsmiths, who make a large array of "authentic period tents" like The Forester, first used by Daniel Beard, founder of the Sons of Daniel Boone in 1905, which later merged with the Boy Scouts of America.