America’s border with Mexico has been generating a lot of words, not just in news and feature pieces but in books as various as William Atkins’s The Immeasurable World and Francisco Cantú’s The Line Becomes A River, a memoir of his years as a US Border Patrol agent. (Cantú also popped up last weekend on BBC2 in Reginald D Hunter’s Songs of the Border, briefing the road-tripping comedian on musicians but without being given a chance to plug his own book.) Porter Fox (what a great byline!) has been preoccupied with a quieter American frontier: the one between the US and Canada. To write his new book, Northland (W W Norton & Company), he spent three years travelling about 4,000 miles from Maine to Washington. He told The New York Times: “I started the way every other northland explorer had for the last 400 years: I packed a canoe, tent, maps and books, and headed for the line.” Outside Magazine has an excerpt from his book on territory in Montana known as the Medicine Line (“named by Native Americans for how the US Calvary magically stopped pursuing them at the US-Canada boundary”).