The Adirondack Forty-Sixers are an organization of hikers who have climbed all forty-six of the traditionally recognized High Peaks of the Adirondack Mountains. They are often referred to just as 46ers.
The first 46ers were brothers Robert and George Marshall, and their guide and family friend Herbert Clark. The Marshalls thought up the idea after spending much of their childhood in the region and examining the collection of Verplanck Colvin maps owned by their father, Louis Marshall. They devised criteria for the high peaks they would climb, choosing any summit that was more than 4,000 feet (1,219 m) above sea level in elevation with at least 300 feet (91.4 m) of vertical rise on all sides or separated from the next closest summit by 0.75 mile (1.2 km). They initially planned to climb only the summits above 4,000 feet (1,200 m), of which there were 42, and did so between 1918 and 1924.
They climbed the 4,000 ft (1,200 m) mountains later, on the suggestion of friends.
At the time that they undertook this goal, there were no trails up many of the peaks, making this a particularly formidable accomplishment. The trio first climbed Whiteface Mountain on August 1, 1918 and finished the 46 with Mount Emmons on June 10, 1925. One of the peaks, Mount Marshall in the MacIntyre Range, has since been named in honor of Bob, and the brook (Herbert Brook) that is the most popular approach has been named after their guide Herbert Clark.
As an organization, the Adirondack Forty-Sixers dates to 1936, when Ernest R. Ryder and Edward L. Hudowalski formed a social club, originally known as the Troy Forty-Sixers, for people who had successfully climbed all 46 of the Adirondack high peaks. The club later expanded its membership, and was formally incorporated by the State of New York as the Adirondack Forty-Sixers in 1948.
Grace Hudowalski was the 46ers club historian for over sixty years.  In 1937 she became the ninth person and first woman to climb all 46 of the Adirondack High Peaks, and in 2014 the mountain formerly known as East Dix was renamed Grace Peak after her due to this accomplishment.  
Some go further and re-climb all the peaks in winter. The winter 46 season is from December 21 to March 21. Winter 46ers are entitled upon completion of the winter 46 to wear the "Winter 46-R" rocker patch. This is a very difficult task due to the severity of winters in the Adirondacks. Some peaks, such as Gothics, can require some technical climbing skill when covered with snow and ice.
As of April 12, 2013, there were 623 winter 46ers and the total membership was 7,806.
- "Finding Aid to The Adirondack Forty-Sixers Records, 1940-2013 (bulk 1970-2013)". New York State Library. New York State Library. Retrieved 24 September 2014.
- "Tribute to Grace Hudowalski 46er #9". Adirondack Forum. March 14, 2004. Archived from the original on 2006-02-14. Retrieved 2011-05-16.
- "Grace Peak Update 11-23-08". Views From The Top. November 23, 2008. Retrieved 2011-05-16.