Mary's Peak (the name used in the blue book, although "Marys Peak" also seems to be used extensively), is a mountain in the coast range, located in Benton County, Oregon. At 4,097 feet, it is the tallest mountain in the coast range.
The Coast Range is a different range than the Cascade Range, being built up of uplifted sedimentary rock instead of being volcanic. The geology of the area is a bit more complicated, but according to the authoritative "Geology of Oregon", the mountain was formed by an intrusion of gabbro that resisted the erosion that is constant in the range. That piece of geology brings us to the second important factor defining the range, and the mountain: the Coast Range of Oregon is very heavy in precipitation. Mary's Peak is a bit further to the east, so the air is not constantly saturated with moisture, but it still gets between 100 and 150 inches of rain a year. Although it does get heavy snowfall, it is not high enough to keep a snowpack past the early spring.
This is perhaps the most important part of Mary's Peak. As far as mountains go, it is one of the easiest and the most accessible. Depending on where you are in the world, a bit over four thousand feet above sealevel (and about the same over the surrounding terrain), may seem quite daunting, or it might seem like a slightly notable hill. As an Oregonian, I am slightly more inclined to the latter. Although Mary's Peak is quite large and it has a truly vast and impressive view from the top, it is also a pleasant hike to the top that can be done without any equipment. In fact, there is even an access road that reaches the top. The top of the mountain is also not notably different from lower elevations, instead being a gently sloping meadow. The area is relatively serene and natural, but there are many trails crossing it and it is not wilderness, at least by my standards. Mary's Peak is a great way to explore the Coast Range for those who don't wish to invest too much time or effort. If the explorer is bored by a measly four thousand feet, they can move on to the harder stuff, like the glaciated Cascade peaks.
There are many things to do and see in Oregon, but if someone happens to be passing through on the highway from Corvallis to the coast, climbing Mary's Peak would be a fun and educational way to spend an afternoon.