A couple of people have noted that there's no one answer. Technologies tend to reinforce one another in unpredictable ways, and we have a logical bias that makes us exaggerate the importance of things that happened within our own lifetimes, and therefore affected our own skiing. What is true is that in each generation something significant changes the sport profoundly.
I've been asked this question before and have written about it a lot. Here's what I would pick for alpine skiing (cross country has its own list):
Prehistoric: Use of pine tar (pitch) to waterproof wooden boats, buildings and skis. It also made wooden skis glide, by repelling water.
1. Camber and sidecut, around 1840. These turned the ski from a plank for shuffling and step-turning to a bit of sporting equipment, useful for running on snow and turning on and in it.
2. Heel strap, also around 1840. Enabled kick-and-glide running, and kept the boot in the binding while jumping. It also helped locate the heel laterally to improve steering. We honor Sondre Norheim for popularizing camber, sidecut and the heel strap, though he may not have been the first to try them.
3. What is certain is that Norheim used these innovations to master the Telemark turn and the Christie.
Steam locomotives reach the mountains -- first mechanized uphill transport (1850 to 1890)
Aerial tramways (1860s) to transport miners and ore, then tourists and skiers, up and down mountains. These made uphill transport pretty common in the Alps long before rope tows came to North America.
3. Metal toe irons, around 1885, improving the skier's edging power dramatically.
4. Carbide steel blades for power saws, around 1880, enabling mass production of skis using hickory and ash. Around the same time, American shoe factories began mass production with industrial sewing machines. Ski equipment becomes a mass-market product.
5. Two-pole skiing (around 1890), for more efficient running.
6. Slalom and downhill (alpine) racing (1901 to 1922), developed by Mathias Zdarsky and Arnold Lunn.
7. Arlberg technique (1907-1914), developed by Hannes Scheider.
5. Steel edges (Rudolf Lettner) and the Kandahar heel-cable latch (Guido Reuge), both in 1928. Enabled power and control on steep and icy pitches.
7. Reinforced sole and instep strap for ski boots, to enable use of the Kandahar cable binding and improve edging power.
8. Laminated skis (1932), making skis lighter, and enabling designers to separate beam flex from torsional flex.
Rope tows and chairlifts (1932 to 1936)
9. Parallel turn (1935) by Toni Seelos
10. Bakelite (phenolic) bases (1936?), made ski bases waterproof.
11. Celluloid base (1944), enabling later development of aluminum skis (1947).
12. Nylon fabric for skiwear (1947)
Snowmaking and grooming (beginning around 1950)
13. Release bindings that really work (1952).
14. Polyethylene bases (1954)
15. Boot buckles (1955), enabling later development of plastic boots.
16. Fiberglass skis (1960)
17. Injection molding for boot soles (1962) and boot uppers (1964), removable and customizable innerboot (1968).
18. Standardized boot soles and binding function (1970s)
19. Fat and shaped skis (1989 to 1992)
I need to point out that many "innovations" are actually revivals or popularizations. For instance, there were experiments with deep sidecut skis in the 1930s (twintips too) but without plastic boots for powerful edging, they didn't work well. We've always had rocker skis (going back to the last ice age) but they didn't make much sense in a modern context until heliskiing became popular. The first aluminum skis were made in the 1920s but without plastic bases they didn't slide well and never achieved mass production.
Anyone really interested in this stuff should explore the ski history timelines at https://skiinghistory.org/history/timeline
Edited by Seth Masia - 11/17/15 at 10:26am