At 2.7 miles, Chicago’s Bloomingdale Trail is more than twice the length of New York’s High Line, and as the final touches are made to it before its June opening, the city has been trumpeting its achievementAt the turn of the 20th century, a copywriter and budding author living in Chicago’s Humboldt Park neighbourhood came up with the concept behind one of the most famous children’s books of all time: a yellow brick road.Some 115 years after The Wizard of Oz by L Frank Baum was published, an alluring pathway (though of a different hue) is about to become reality – just one block north of his Humboldt abode.