Heralded as a sport in England in the late 1880s after the (well publicised) solo first ascent of the Napes Needle by Walter Parry Haskett Smith, rock climbing attracted increasing numbers of participants. An early benchmark approaching modern levels of difficulty was the ascent, by O. G. Jones, of Kern Knotts Crack (VS) in 1897. Jones was attracted to the new sport by a photo of the Needle in a shop window in the early 1890s. By the end of the Victorian era as many as 60 enthusiasts at a time would gather at the Wastwater Hotel in the Lake District during vacation periods.
Inspired by the efforts of late 19th century pioneers such as Oskar Schuster (Falkenstein, Schusterweg 1892), by 1903 there were approximately 500 climbers active in the Elbe Sandstone region, including the well-known team of Rudolf Fehrmann and the American, Oliver Perry-Smith; their 1906 ascent of Teufelsturm (at VIIb) set new standards of difficulty. By the 1930s there were over 200 small climbing clubs represented in the area.
The solo first ascent of Die Vajolettürme in 1887 by the 17-year-old Munich high school student, Georg Winkler, encouraged the acceptance and development of the sport in the Dolomites.
As rock climbing matured, a variety of grading systems were created in order to more accurately compare relative difficulties of climbs. Over the years both climbing techniques and the equipment climbers use to advance the sport have evolved in a steady fashion...
1492 : Antoine de Ville ascends Mont Inaccessible, Mont Aiguille, a 300-meter rock tower south of Grenoble, France. Under orders from his king, he used the techniques developed for sieging castles to attain an otherwise unreachable summit. The ascent is described by François Rabelais in his Quart Livre.
1786 : The first ascent of Mont Blanc is often referred to as the start of mountaineering’s “modern era”. It took another century before history documents the use of devices similar to today’s fixed anchors: pitons, bolts and rappel slings.
Napes Needle, first climbed by W P Haskett Smith in 1886
By the 19th century, climbing was developing as a recreational pastime. Equipment in the early 19th century began with an alpenstock (a large walking stick with a metal tip), a primitive form of three-point instep crampon, and a woodcutter's axe. These were the tools of the alpine shepherd, who was shortly to move from guiding sheep to guiding men, a much more lucrative enterprise. With time the alpenstock and the axe were combined into one tool: the ice-axe. Add a large, thick (and weak) rope, to help the client climb, and guide and novice were off to the mountains.
1893 : Devils Tower is first summited by ranchers William Rogers and Willard Ripley through the use of wooden spike pounded into a crack and then connected with a rope. After 6 weeks they summited on the Fourth of July.
1910 to 1914 : Hans Dülfer suggests using equipment to ascend otherwise unclimbable rock, devises dülfersitz rappelling technique.
1914 : Paul Preuss, an advocate of Free climbing, coins the term "artificial aid" to describe the use of mechanical aids to progress up a rock. His rule number four (of six) stated: "The piton is an emergency aid and not the basis of a system of mountaineering."
Note: The two principal uses of pitons on an ascent are as protective safeguards (not used for actual hand or footholds - climbers refrained from putting weight on them except in the event of a fall) and as direct aid (used to physically assist in ascending a steep or overhanging slope rather than merely as protection). Climbers like Paul Preuss and Geoffrey Winthrop Young argued strongly against direct aid, but others of that era, including Hans Dülfer and Tita Piaz, advocated using such devices as artificial aids in order to climb otherwise unscalable walls. After World War I most European climbers chose to employ artificial aid when necessary. However, from the beginning days of rock climbing as a sport, through the 1940s, another form of artificial assistance was at times employed by teams of two or more climbers: the shoulder stand. From our current perspective it seems odd that many of those climbers who strenuously objected to hanging on a piton found the shoulder stand to be quite acceptable. Occasionally, historical climbing photos, (e.g., ) illustrate this strategy, which arose from the perception that ascending a route was a team effort, with two climbers constituting one natural climbing unit. Something to keep in mind when reading of very early climbs in the 5.8 to 5.10 range.
1914 : Siegfried Herford and companions climb the Flake Pitch on Central Buttress of Scafell (5.9), England's hardest climb at the time.
1920s - 1930s : Robert L. M. Underhill and Miriam Underhill (Miriam E. O'Brien) - One of the early rock star climbing couples. Robert is remembered for introducing European climbing techniques to the west coast of the US through an article in the 1931 Bulletin of the Sierra Club.
1922 : Hans Rost and party ascend the Rostkante on Hauptwiesenstein (5.10d), Elbe Sandstone Mountains, the world's hardest climb at the time
1922 : Paul Illmer and party ascend the Illmerweg on Falkenstein (5.10b), Elbe Sandstone Mountains
1923 : Willo Welzenbach creates the standard numerical rating system for the difficulty of a route (Grades I to VI) 
1925 : Solleder and Gustl Lettenbauer climb the Northwest Face of the Civetta in a day, a 3800-foot 5.9 route in the Dolomites, using only 15 pitons for protection and belays.
1931 : Emilio Comici and the Dolomites. Comici is the inventor and proponent of using multi-step aid ladders, solid belays, the use of a trail/tag line, and hanging bivouacs. Pretty much the origin of big wall climbing and techniques. He uses them to good purpose with an ascent of the 26 pitch, 4000 foot Northwest Face of the Civetta.
1946 : John Salathe, at the age of 46, attempts to rope-solo aid the first ascent of the Lost Arrow Spire, one of the most exposed features in Yosemite Valley. (The protection bolt he places on that attempt was the first, or one of the first, in the valley.) He is also known for his forged pitons made from the axle of a Model A Ford.
1957 : Layton Kor appears in the climbing community of Colorado and gains recognition as a notable climber. Makes landmark ascents, including Redguard, The Bulge, T2, Naked Edge, X-M, and the Yellow Wall. Kor is noted as one of the key forces behind the progression of climbing in the west.
1958 : Warren Harding and team climb the 3,000 foot Nose of El Capitan using siege tactics, taking a total of 45 days over an extended period. Almost entirely aid climbing, with many bolts (125), the climb is given worldwide recognition.
1959 : Ray Northcutt free climbs Direct Start to Bastille Crack (5.10d) in Eldorado Canyon, Colorado. This was the hardest free climb in North America at the time (not including John Gill's ropeless climbs of long boulder problems done earlier in the decade).
2014: January 15, Alex Honnold became the first person to free-solo El Sendero Luminoso (the Shining Path), a climbing route in El Potrero Chico, Mexico.
2015: March 7, Chris Sharma made the first ascent of El Bon Combat at Cova de Ocell near Barcelona, at a proposed grade of 5.15b/c, one of the five hardest routes in the world.
2015: March 17, Ashima Shiraishi climbed Open Your Mind Direct, in Santa Linya, Spain at only 13 years old. Originally rated as a 9a (5.14d), there has been some controversy over the rating due to a broken hold at the end of the route. Some claim the broken hold bumps the rating to a 9a+ (5.15a).
2015: Tommy Caldwell and Kevin Jorgeson are the first to free climb "Dawn Wall", Yosemite Valley, California. (5.14c)
2017: February 26, Margo Hayes becomes the first woman to redpoint a 9a+ (5.15a) by climbing La Rambla at the Spanish crag Siurana.
2017: June 3, Alex Honnold free solos the 3,000 foot wall of El Capitan in 3hrs and 56mins
2017: September 3, Adam Ondra climbs Silence in Flatanger, Norway, suggesting a grade of 9c (5.15d)