Whitman Mission, and the forty floods you can count

Whitman Mission sits on 139 acres west of the Blue Mountains, where the Walla
Walla River meets Mill Creek. The 1836 mission of Marcus and Narcissa Whitman
stood here, and the deaths that followed — driven by the ignorance, racism and
ethnocentrism the American Board of Commissioners for Foreign Missions brought
to the Weyíiletpuu (Cayuse) and Walúulapam (Walla Walla) — became a catalyst
for American expansion into the Pacific Northwest.

It is Cayuse homeland, and the site is a memorial as much as a museum. It was
made Whitman National Monument on 29 June 1936 and redesignated a national
historic site on 1 January 1963. The restored mill pond, an apple orchard, the
Mission House site, the blacksmith shop and the grist mill are all here.

What is under it

**One of the largest continental flood basalt eruptions in the Western
Hemisphere.** Between about 17 and 6 million years ago, the Columbia River
Basalt Group flooded roughly 160,000 km² of the Columbia Plateau across
Idaho, Oregon and Washington. Those flows are buried here, but they are the
foundation.

What is on top of it, and why it is striped

During the Pleistocene, glacially dammed lakes formed, failed catastrophically,
and sent floodwater across this region — where it backed up behind **Wallula
Gap**.

Water slowing abruptly drops its load in order: gravel and sand first, then
silt, then clay. So each flood left one graded couplet.

It happened at least forty times. The result is the Touchet Beds —
Pleistocene rhythmites, one band per catastrophe, stacked where you can count
them.

Where it fits

Whitman Mission is part of the
Columbia Plateau physiographic province
and shares its history with a region far beyond the park.

The Geologic Resources Inventory
produces digital geologic maps and reports for more than 270 natural resource
parks — a scoping summary recording what the mapping plan should cover, GIS
map files with a usage guide, and a report tying the maps to the park's
setting, features, management issues and history.

Sources

Written from the National Park Service's Geodiversity Atlas entry for Whitman
Mission National Historic Site, a work of the United States government in the
public domain. Flood basalt and Touchet Beds from Graham (2014b); park history
from the National Park Service (2016a, 2017).