Profile America — Thursday, April 10th. The need to pay a $15 debt sparked one of the most useful of inventions, patented on this date in 1849. Walter Hunt, a mechanic in New York, owed the debt. While he thought about how to raise the money, he fiddled with a small piece of wire. Finally, he bent the wire with a twist in the middle, creating a spring, and formed a clasp at the other end, to guard the point of the wire. He had invented the safety pin. Hunt called his device a "dress pin," and sold his rights to it for $400, little realizing that its utility would be enduring and lucrative. Manufacturing pins, needles, buttons and other fasteners is a near-$900 million a year business in the U.S., employing about 5,500 people. You can find current data on the country's economy by downloading the America's Economy mobile application at<www.census.gov/mobile>.