The Workmans' exploration of the Rose Glacier and the 45-mile-long (72 km) Siachen Glacier in Baltistan around Masherbrum in 1911 and 1912 was the most important achievement of their careers because it was the widest and longest subpolar glacier in the world and at the time, the least explored and accessible glacier as well. For two months, the Workmans explored the 45-mile glacier, climbed several mountains, and mapped the area. They spent the entire time over , the high point being Indira Col, which they summitted and named. On this expedition, one of their Italian guides fell into a crevasse and died; Fanny was lucky to escape. The others were badly shaken but decided to carry on. Fanny led them across the Sia La pass () near the head of the Siachen Glacier and through a previously unexplored region to the Kaberi Glacier. This exploration and the resulting book were among her greatest accomplishments. As she wrote in her book about the trip, Two Summers in the Ice-Wilds of Eastern Karakoram, she organized and led this expedition: Dr. Hunter Workman accompanied me, this time, in charge with me of commissariat and as photographer and glacialist, but I was the responsible leader of this expedition, and on my efforts, in a large measure, must depend the success or failure of it. At one 21,000-foot (6,400 m) plateau, Fanny unfurled a Votes for Women newspaper and her husband snapped an iconic picture. They took trained Alpine guides and surveyors including Grant Peterkin and Surjan Singh, whose contributions ensured that, unlike numerous other maps the Workmans helped create, their map of the Siachen Glacier remained unchallenged for many years.