I have been carrying these on my phone for a while. Some honorable mentions below.
Elk Mountain, OR 6 towards Tillamook
An excellent fun hike with great proximity to Portland and PDX suburbia lies on OR 6, with an elevation gain of approximately 1900 ft in 1.4 miles. It is an excellent alternative to stepper or elliptical. Be prepared for the more challenging levels.
I would estimate the hike at 90 mins to the summit while the return at 45 mins to an hour. An interesting thing is the log book maintained at the summit where you can print and date your name (Elk achiever’s log). I have hiked this at least 10 times through pretty much every season, with spring or fall as the best time to hike and summer as the fun time (dry and lose soil, makes some lengths of the trail quite fun). You were warned! 🙂
Kings Mountain on OR 6 towards Tillamook
Very next to Elk Mountain is Kings Mountain – elevation gain of 2500 ft in 2.4 miles. The views are similar to Elk Mountain, while Elk is comparatively more exposed, Kings relatively trails through dense forest.
Mitchell Point on I-84 E towards Hood River
A short hike gaining around 1100 ft in 1.2 miles, should not take more than 45 mins to the top and 20-25 mins to run down the hill. It is quite pretty from up there.