Why do golf courses have 18 holes?

Golf courses didn't always have 18 holes. The number of holes used to vary widely: 11, 22, 24, etc. As with most golf tradition-related questions, the reason why 18 became the standard goes back to <a href="http://www.standrews.org.uk/">St. Andrews</a> of Scotland, the granddaddy of all golf courses. The <a href="http://www.usga.org/questions/faqs/usga_history.html#8">original course</a> at St. Andrews (dating back to the 15th century!) consisted of 11 holes along a narrow strip of land next to the sea. Each hole was played twice, for a total of 22. In 1764, two of the holes were judged to be too short, so the course made the switch from 22 to 18 holes (nine holes played two times each). In 1858, the Royal & Ancient Golf Club of St. Andrews, not an institution to be trifled with, issued an <a href="http://www.britishgolfmuseum.co.uk/faq.asp">official decree</a> that one round of links, or 18 holes, constituted an official match. Other courses pretty much followed suit, and by the ...  more