While passing through what is now eastern Washington, Stanley illustrated Old Fort Walla Walla looking down the Columbia River towards Wallula Gap, where the Columbia River cuts through the Horse Heaven Hills. This gap was sculpted into spectacular vertical basalt cliffs by the Missoula Floods during the last glacial period. During the floods this was the biggest choke point with flood waters backing up at this narrow gap and inundating most of the Yakima River valley and Walla Walla River valley with water nearly 1,000 feet deep. Stanley's rendition of the gap includes the Twin Sisters, two matching blocks of basalt that are located at the north end of the gap.
Twin Sisters, a result of differential erosion of Columbia River Basalt Units
Wallula Gap today near the old fort site
The Fort was a key cross "roads" in the trade routes. The gap provided the passage on the Columbia through the Horse Heaven Hills and then down the Columbia to the Columbia Gorge through the Cascade Range and then the ocean. Routes east would follow the Walla Walla River or up the Walla Walla to the Touchet River for an overland route to Snake River and Clearwater River junction. This later route was used by Lewis and Clark on their return east. Routes north included the Columbia as well as an overland trail route through the Palouse. And a short distance up the Columbia led to the Yakima River valley.
The fort was originally erected by the North West Company in 1813. Donald MacKenzie formerly of the Astorian company oversaw the construction and opperated the fort. He called the fort, Fort Nez Perce to honor the Nez Perce, the dominant tribe of the region. As far as I know there was never any trouble at the fort. The Hudson Bay Company absorbed the North West Company in 1821 and continued operating the fort up till 1855 when Washington Territory became part of the United States.
The original fort location became submerged under the slack waters created by McNary Dam on the Columbia. With the coming of railroads, the site lost its position as a trading center with activity having shifted towards the more hospitable Walla Walla or other sites along rail lines. A small railroad town developed and remains nearby.
Even today, few people live in the area even though there is a large paper mill and meat packing plant. It is a windy hot place in the summer with gravelly soils. I spent a winter as a meat cutter at the meat packing plant replenishing college funds during my undergraduate days. Like nearly everyone else at the plant I commuted from the Tri-City area and by all appearances most workers at the paper mill and meat packing plant continue to commute from outside the immediate area. The fact that the paper mill is a bit stinky and combined with odors from the feed lot that was adjacent to the meat plant may have played a role in this spot not attracting many residents.