Up until the early part of the 20th century, horses were fundamental to both transportation and farming in the United States. The annual Plow Play Day harkens back to that time, with harnessing and horse-drawn plowing demos, carriage rides, and the chance to see Clydesdale, Percheron, Shire, and Belgian draft horses. Visitors can also get a look-see at an Early Day gas engine and watch blacksmiths working at a forge. The annual event will be held on May 19, 10 a.m.–3 p.m., at the Jack London State Historic Park in Glen Ellen. Admission is free; parking is $10.