The Turn-of-the-20th Century snapshots of
the Blake & Clark Families
National Park Cavalry soldier in uniform, 1906
While Adeline didn't identify the photographs of the army troop passing by, a little research of the flag being carried and the uniform design helped determine these were members of a U.S. Cavalry unit, Between the late 1890s and 1916, the same Cavalry units protected the National Parks. Considering the photographs of the western trip in 1912 included Adeline and Lucian being in a national park, it makes sense that the photos included were from that experience.
1899 image of the Troop F, 6th Cavalry in Yosemite
A Brief History of Yosemite National Park and the use of National Cavalry.
As Yosemite Valley became a popular tourist destination in the 1850s and 1860s, there was a need for some form of protection from human thoughtless actions. Having camp fires left going, people carelessly leaving their waste, and the influx of billboards all threatened the natural space.
In 1864, President Lincoln and then Govenor Low signed bills for protecting the lands; in 1890, a Federal grant to increase the amount of land and to name it a National Park, following the example of Yellowstone Park 20 years before.
The answer for protection of both land and people in both parks was to assign a cavalry troop detail, which happened in 1891. From 1891 until 1916, the protection of National Parks were the purview of the Army. The creation of the National Park Service in 1916 replaced the U.S. Army troops with the National Park Rangers.