In 1906, Berkshire County began survey and construction of another approach, the first direct route from the south to the summit.
It was opened to the public on September 16, 1907, running "through six farms ... passing Round's Rock, a fine view point, and throughout its entire distance affords unsurpassed views of Berkshire hills and valleys lying to the south and west of the reservation".
Afterwards the Commission turned its attention to the foot trail development, and by 1913 it was able to boast that 17 trails existed on the mountain.

By 1929, the Appalachian Trail route up Mount Greylock was first cut, and most of the Massachusetts section route was complete by 1931.
Due to disputes between the local Berkshire Hills Conference trail group and both the Appalachian Trail Conference and the Appalachian Mountain Club Berkshire Chapter, the trail was in jeopardy of growing back in until the local Mount Greylock Ski Club assumed maintenance in 1937.

The greatest period of development on Mount Greylock occurred in the 1930s.
The Massachusetts (Veterans) War Memorial Tower on the summit was constructed (1931–32).
 The Civilian Conservation Corps (CCC) 107th Company, MA camp SP-7, from 1933-1941 made extensive improvements on roads, trails, scenic vistas, firebreaks, forest health improvement, and recreation area development.

Some of the more significant CCC features included development of the road system (gravel surfaced) to accommodate automobiles, Adirondack lean-to shelters, the Thunderbolt Ski Shelter, and completion of Bascom Lodge.
As a result of increased popularity of winter recreation and downhill skiing, the Mount Greylock Ski Club initiated a plan to create a challenging ski run on Mount Greylock.
The planning skills of Dwight J. Francis and Western Massachusetts Winter Sports Council, including input from Williams, Amherst, Smith, Mount Holyoke, and Massachusetts State Colleges, Greenfield Outing Club, and the Green Mountain Club, resulted in the CCC building the Thunderbolt Ski Trail in 1934 (named for its resemblance to a Revere Beach, MA, roller coaster).
The lower section of the Thunderbolt Trail was relocated in 1936 by Charles L. Parker.
This ski trail was rated Expert-Class A by the United States Eastern Amateur Ski Association (USEASA, today the United States Ski and Snowboard Association) and later host site for the USEASA Championship Races in 1938 and 1940.
The trail was used for numerous competitive downhill ski races up until 1959.

Based on the popular response to winter recreation at Mount Greylock, a New York-based group expressed interest to the Greylock Commission to develop a cable tramway and downhill ski area on the southwest portion of mountain in 1941.
The proposal, though defeated, initiated an ongoing debate between the use of Mount Greylock (State) Reservation for commercial development and open hunting versus conservation purposes.

In October 1966, following years of legal disputes over the Greylock Commission's perceived abuses of allowing public land for commercial use, a conservation group called the Mount Greylock Protective Association led a campaign that transferred ultimate responsibility for management and operation the mountain from Berkshire County to the state park system.
In 1906, Berkshire County began survey and construction of another approach, the first direct route from the south to the summit. It was opened to the public on September 16, 1907, running "through six farms ... passing Round's Rock, a fine view point, and throughout its entire distance affords unsurpassed views of Berkshire hills and valleys lying to the south and west of the reservation". Afterwards the Commission turned its attention to the foot trail development, and by 1913 it was able to boast that 17 trails existed on the mountain.
By 1929, the Appalachian Trail route up Mount Greylock was first cut, and most of the Massachusetts section route was complete by 1931. Due to disputes between the local Berkshire Hills Conference trail group and both the Appalachian Trail Conference and the Appalachian Mountain Club Berkshire Chapter, the trail was in jeopardy of growing back in until the local Mount Greylock Ski Club assumed maintenance in 1937.
The greatest period of development on Mount Greylock occurred in the 1930s. The Massachusetts (Veterans) War Memorial Tower on the summit was constructed (1931–32).  The Civilian Conservation Corps (CCC) 107th Company, MA camp SP-7, from 1933-1941 made extensive improvements on roads, trails, scenic vistas, firebreaks, forest health improvement, and recreation area development.
Some of the more significant CCC features included development of the road system (gravel surfaced) to accommodate automobiles, Adirondack lean-to shelters, the Thunderbolt Ski Shelter, and completion of Bascom Lodge. As a result of increased popularity of winter recreation and downhill skiing, the Mount Greylock Ski Club initiated a plan to create a challenging ski run on Mount Greylock. The planning skills of Dwight J. Francis and Western Massachusetts Winter Sports Council, including input from Williams, Amherst, Smith, Mount Holyoke, and Massachusetts State Colleges, Greenfield Outing Club, and the Green Mountain Club, resulted in the CCC building the Thunderbolt Ski Trail in 1934 (named for its resemblance to a Revere Beach, MA, roller coaster). The lower section of the Thunderbolt Trail was relocated in 1936 by Charles L. Parker. This ski trail was rated Expert-Class A by the United States Eastern Amateur Ski Association (USEASA, today the United States Ski and Snowboard Association) and later host site for the USEASA Championship Races in 1938 and 1940. The trail was used for numerous competitive downhill ski races up until 1959.
Based on the popular response to winter recreation at Mount Greylock, a New York-based group expressed interest to the Greylock Commission to develop a cable tramway and downhill ski area on the southwest portion of mountain in 1941. The proposal, though defeated, initiated an ongoing debate between the use of Mount Greylock (State) Reservation for commercial development and open hunting versus conservation purposes.
In October 1966, following years of legal disputes over the Greylock Commission's perceived abuses of allowing public land for commercial use, a conservation group called the Mount Greylock Protective Association led a campaign that transferred ultimate responsibility for management and operation the mountain from Berkshire County to the state park system.
Mount Greylock