Sport and mode of transportation involving moving over snow on a pair of long flat runners (skis) attached to shoes or boots. Skiing was born in northern Europe; the oldest skis, found in Russia, are some 6,000 years old. The earliest skis were often short and broad. The first written references to skiing come from the Han dynasty (206 BC–AD 220) and describe skiing in northern China. Skiing was used in warfare in Scandinavia from the 13th century or earlier to the 20th century. The earliest mode of skiing developed into the sport now called cross-country skiing. Competitive cross-country skiing began in Norway in the 1840s and had reached California by the 1860s. Improvements on primitive bindings c. 1860 led to greater popularity of recreational skiing. Ski-jumping competitions date from the 1870s. Downhill skiing was limited by the need to climb the hill before or after skiing down; the building of ski lifts began in the 1930s. Skis were originally made of a single piece of wood, usually hickory; laminated construction began in the 1930s, plastic running surfaces were introduced in the 1950s, and no wood has been used in the construction of downhill skis for several decades. The business of skiing began its serious growth in the 1930s and became explosive in the 1950s and '60s; huge resorts now dot the Austrian, Swiss, and Italian Alps, the Rocky Mountains, and other mountainous regions. See alsoAlpine skiing.