Big Mountain is part of Whitefish Ski Area and in the summer you can take the chairlift to the top ($20) and hike, ride bikes and activate Big Mountain. The communication towers that sit atop the summit are easy to see from the top of the chairlift and it's only a short quarter mile walk up the graded road to the top.
This summit is a progressively more difficult climb as you ascend. The activation is challenging but rewarding. The route I took starts with an easy well trafficked trail, but the second part of the ascent has no trail and involves navigating through the Angell Basin which consists of areas of large granite boulders.
Follow any road map to Soda Mt. Rd or Hobart Bluff TH off of Hwy 66. You will follow the gravel road down past Hobart Bluff Trailhead, there is a parking area and restroom here. Go on past the trailhead aways until you reach the gated driveway for Soda Mountain on the right. It is a 1.5 mile walk up to the summit using the road. Minimal parking area as you will be in wilderness and there is very few pullouts to park in.
Henline is a relatively low traffic hiking trail in the Opal Creek Wilderness. It boasts rhododendrons, a mostly-well-maintained trail, and reasonably consistent gains. The hike is entirely on public right of way, and can be accessed via North Fork Santiam Road and NFDR 2207 from Hwy 22 out of Salem. Turn left on North Fork Santiam Road about 22 miles from I-5, then drive straight. Eventually this road turns to a moderate gravel road, followed by a fork between 2207 and 2209. Take the left fork and head uphill a ways. You'll pass the more popular Henline Falls Trailhead.
Flattop Mountain is a drive-up for those with capable high clearance vehicles. And maybe for those ready to buy new tires - which was required of us - as the road was steep with sharp rocks.
Here's a nice summit with a trail to the top, about 5 miles RT and more elevation gain that you might have wanted at 1800 feet - but know that it's worth it. A bit obscure perhaps outside of huckleberry season, you might not see many folks at other times. The views of Mt. Adams are fabulous.
Elk Mountain is in the Olympic National Park and accessible from a well-maintained forest service road named Obstruction Point Road. The road is not open all year, so check park conditions before you go. The summit is attainable by taking the Obstruction Point Trail and then making the easy traverse up to the base of a large rock formation. A quick stairstep up the rocks brings you to the summit. Total hike from parking to summit is about 1.5 miles.
Summit 5645 (Hurricane Ridge) is in the Olympic National Park and accessible from a well-maintained forest service road named Obstruction Point Road. The road is not open all year, so check park conditions before you go. There is no established trail to this SOTA summit, but it is quite straightforward to follow the ridgeline to the summit and does not require bushwhacking.
On-Trail, 2.5 miles, +2,240 ft
Baldy Mountain is a locally popular on-trail hike to one of the high points in the East Pioneer Mountains. The foundation of the old fire lookout provides some shelter in the event of windy conditions. We saw one other party on the mountain on a nice Saturday during the summer.
NC-009, Sheridan Peak, is a good first-time activation destination. It is an easy half-mile hike (about 300' climb) from the parking lot to the summit, which is broad and flat; lots of good spots to set up. The summit is wooded and shady with a fair amount of old growth, so there are no views. Cell data service is spotty. I managed to spot myself once with SOTA GOAT though I tried four or five times. Two way APRS coverage was excellent and I spotted myself on aprs using a VX8DR.