While receiving training as an engineer at this latter school, Folsom's health deteriorated until his career path was drastically changed by moving west as advised by his physician.
[3] Folsom led an expedition of the land that would become Yellowstone National Park beginning on September 6, 1869, with Charles W. Cook and William Peterson.
[1] The expedition started from Diamond City and included the following routes in chronological order: Trail Creek, Yellowstone River, Tower Falls, Lamar Valley, Grand Canyon, and more.
[4] These thoughts were planned to be included in a July, 1870 publication of the magazine, Western Monthly, but these parts were omitted by the editors who intended to only show what physical features of the park were explored and described.
[6] Around 1873–1875, Folsom returned to New Hampshire, married his wife, Lucy Jones, in 1880, and moved back to Montana to manage a ranch with her near Smith River.