Bonneville Dam and Beacon Rock

long dam crossing the river with a monolithic rock far in the background

Photo by J. Agee, © 1999 VIAs Inc.

View west from above Bonneville Dam. The hazy silhouette of Beacon Rock is visible at photo center, seemingly dwarfed by diaphanous towers bearing electrical transmission lines.

Beacon Rock

Tall columns of basalt rock

USGS Photo by Lyn Topinka, June 15, 2003.

When lava cools it fractures into columnar basalt—pentagonal columns of rock from one to four feet in diameter.5

There are no journal entries by Meriwether Lewis for these days that might help explain Clark's use of the word "Beaten."1 The photograph above, however, suggests that Lewis may have seen it first from upriver, pointed it out to Clark, and given it the name. Clark's word, then, may have represented not a spelling error, but a misunderstanding of what Lewis said, for the following spring Lewis himself wrote of the rock, calling it "the beacon rock." Seven years later, while editing the captains' journals for publication, Nicholas Biddle seemed puzzled by the inconsistency, and it may be that Clark corroborated Lewis's correction, for Biddle inserted the word Beacon in Clark's manuscript, and used it in his paraphrase.2

Patrick Gass, whose journal appeared in 1807, didn't mention the place, and Clark's map, published with the first edition of the captains' journals in 1814, didn't show it. Those omissions, plus the rush of commercial fur trading, doomed the explorers' name for the landmark to a short life. Alexander Ross, a member of the Astor fur-trading expedition, who camped near its base on July 27, 1811, evidently was reminded of a familiar landmark back in Scotland, for he dubbed it Inshoach Castle.3

In mid-October of 1835 the Presbyterian missionary Samuel Parker passed through the neighborhood, and evidently heard it called Pillar Rock, since he didn't take credit for originating the name. Incidentally, Parker recognized it as a basaltic formation, and one of the astonishing wonders of volcanic operations, reflecting advances that the science of geology had made by that date.4


1. In fact, there are no entries by Lewis between September 22, 1805, in which he expressed his pleasure in having "tryumphed over the rocky Mountains," and December 1, when he made some botanical notes during his quest for a winter campsite.

2. Nicholas Biddle, ed., History of the Expedition Under the Command of Captains Lewis and Clark . . . (2 vols., Philadelphia: Bradford and Inskeep, 1814).

3. Alexander Ross, Adventures of the First Settlers on the Oregon or Columbia River . . . (London: Smith, Elder and Co., 1849), p. 107.

4. Samuel Parker, Journal of an Exploring Tour Beyond the Rocky Mountains . . . in the Years 1835, '36, and '37 (2nd ed., Ithaca, NY: Published by the Author, 1840), p. 143.

5. Photo from the USGS Beacon Rock Photo Files, at http://volcanoes.usgs.gov/observatories/cvo/Historical/LewisClark/volcan... (accessed July 2015).

Last revision: 03–2017