[3][4] The Saddle Mountains was an important transportation corridor for Native Americans in the region, including the Yakama, with people passing over then to get between the Yakima Valley to the north and traditional fishing grounds along the Columbia River to the south.

The volcanic region stretches a north–south distance of approximately 45 mi (72 km) from near Goldendale, Washington in the south to include part of the Yakama Indian Reservation in the north.

[8][3] The highest point in the volcanic complex is Jennies Butte, a cone that erupted dacite on the north end of the field with a peak elevation of 6,408 ft (1,953 m) above sea level.

[1] Within the ridge area north of Goldendale and west of Satus Pass, the highest point is the remains of a basaltic shield named Indian Rock with a summit at 5,820 ft (1,770 m) above sea level.

[3] The region lies adjacant to the eastern foothills of the Cascade Mountains with more arid conditions than points a short distance to the west due to the rain shadow effect.

[10][11] The crest of the highland area about 13 miles (21 km) north of Goldendale forms the southern boundary of the Yakama Indian Reservation.

The Sun visited the Simcoe Mountains, termed Wahkshum, first each morning followed by the Goat Rocks, referred to as Plash-Plash, and Mount Adams (Pahto) third.

[15] The region was largely used as a travel corridor between the Yakima Valley and traditional fishing grounds on the Columbia River, including the now flooded Celilo Falls.

[16] The highland area itself was fairly remote and travelers avoided it during the winter months due to frequent blizzards and other adverse weather conditions.

[24] Rotation of the North American Plate in the Pacific Northwest during and after the Columbia River Basalt Group flows led to the rise of the Yakima Fold Belt, a series of east–west ridges upon which the Simcoe Mountains lie, most notably the western end of the anticline that created the Horse Heaven Hills that extend eastward toward Kennewick.

[3] The rise of these ridges significantly disrupted the path of the Columbia River, which formerly flowed through the area but was absent by the time the volcanic field formed.

[26] Evidence of glaciation has not been observed in the area, likely owing to the highlands' comparatively low elevation and location to the east of the crest of the Cascade Mountains.

[3] Some of the volcanic activity in Simcoe Mountains happened at the same time as eruptions of Goat Rocks to the northwest and the Boring Lava Field near Portland, Oregon.

Mid elevations experience more rainfall and are a little cooler, though still largely display grassland flora including wildflowers like elkhorns clarkia and scabland wild buckwheat while the ridges and mountain tops can be forested with Ponderosa pine, western juniper, and Douglas fir.

[15] Small streams produce productive riparian zones even in low elevations with large trees including black cottonwood present despite arid conditions.

Many streams may dry up on the surface during the summer but continue to flow underground because the porous nature of the rocks allows for groundwater movement in the region.

[31][32] Wild turkey can be found on the south slopes of the highland area north of Goldendale and forest grouse are present in riparian zones and disused logging roads.

[30] Water in the mountains is relatively free from pollutants owing to the lack of permanent human habitation and farming activities in the forested region.