John Middendorf
John William Middendorf IV (November 18, 1959 – June 21, 2024) was an American big-wall climber, climbing gear designer, and writer. He climbed some of the hardest walls in Yosemite in the 1980s, and in 1992 he and Xaver Bongard completed the first ascent of the East Face of Great Trango Tower. He also founded A5 Adventures, a company that made portaledges and other big-wall gear.
Middendorf grew up with climbing discovered at summer camp when he was fourteen. He studied mechanical engineering at Stanford University, earning a BS in 1983, and later pursued studies in design and teaching. After college he moved to Yosemite, where he joined the search-and-rescue team and helped push the development of safer, more reliable portaledges. A near-fatal fall on Half Dome inspired him to improve portaledge designs.
In 1986 he left Yosemite and started A5 Adventures Inc. in Flagstaff, Arizona, to design and manufacture portaledges and other big-wall equipment. The gear he developed was built to withstand severe alpine weather, including in the Himalayas and Karakoram. In 1992 Middendorf and Bongard completed the Grand Voyage, a climb of the Great Trango Tower’s East Face, one of the world’s most challenging big-wall walls. The ascent used A5 portaledges and took about 15 days of climbing and several days to descend.
A5 Adventures was acquired by The North Face in 1997. Middendorf stayed on as a Senior Product Manager for a number of years before leaving the company to pursue writing and guiding tours in the Grand Canyon. There he met his wife, Jeni Middendorf.
In 2003 he began studying fabric materials engineering in Sydney, Australia. While there and later in Tasmania, he continued climbing, taught in the Tasmanian school system, and supported environmental activism, even providing portaledges for forest-protection campaigns. He moved to Tasmania in 2006 and remained active in climbing and education.
In 2016 Middendorf started building climbing gear again under a new brand, D4. He redesigned portaledges, creating models like the Delta2p and Delta3p, the first “foot-out” portaledge designs, and also built the D4 Trapezium shelter. He made much of his design work open-source on Bigwalls.net, including a DIY Activist Ledge for non-violent protests.
Middendorf wrote extensively about climbing and activism. Between 2021 and 2023 he published Mechanical Advantage: Tools for the Wild Vertical, a two-volume history of climbing tools and techniques.
He died in his sleep on June 21, 2024, at age 64, while visiting family in Rhode Island. He is survived by his wife Jeni and their two children.
This page was last edited on 3 February 2026, at 14:38 (CET).