My evidence for them being on an east-west line is from a camping trip on Adams on the September equinox some years ago at Crystal Lake. On the equinox the sun sets due west, and I watched it set into the crater of MSH.
But the center of the crater of MSH is not it's summit - that is on the southern rim, so that explains how the summit of MSH is a bit farther south. Something approximating the crater center (especially if there were a northern rim) looks like it would be as close to the same latitude of Adams as I can tell in that map.
Yeah, earlier I was measuring between marked points on the chart, which would make it appear that St. Helens is slightly SW of Adams. Using the scales and tracing west from the marker on Adams' eastern peak (12276') over the St. Helens crater (above the 8365' peak marker at St. Helens) then they do line up east-west, both on screen and on the paper chart. The east peak is at the center of Adams as it appears there.
Note there may also be a slight discrepancy because aero sectionals are a 1:500000-scale Lambert conformal conical projection and I'm measuring in a straight line with a wooden ruler, but it's negligible for the purposes of this discussion. For the national combined slippy chart on Skyvector, they reprocess it to a pseudo-Mercator projection so the sections all flow together seamlessly.... and even there the two mountains line up.
https://skyvector.com/?ll=46.2397021307 ... 301&zoom=2
The entire eastern half of Mt. Adams (and all the way to U.S. 97 and beyond) is on Yakama Nation land.
Ah. I had been under the impression that the reservation was a bit further east. Thanks for the clarification.