for most people, smith rock is best known for its climbing. it was home of the hardest route in the states for quite a while, the notorious east face on monkey face. however, because of its scenic location and easy access, it also is great for trail running. the trail around smith rock itself can be a bit crowded, but the trails a bit further away are empty and the highest peak in that area, gray butte, offers great panoramic 360 degree views of central oregon.
for an easy run inside smith rock state park, you can take the trail around smith rock, and then the aptly named misery trail over misery ridge, which ends right ar the bridge where you started. this loop will take about 40min of easy running, from the bridge to the bridge. we ran it clockwise, but it may be nicer to run counterclockwise, because the east side of misery ridge is quite steep and slippery, and running up this terrain is probably nicer than running down. either way, it's a great loop and even though the trail to misery ridge is steep, it only takes about 10min to get up, so it's not all that hard.
for a longer and more remote experience, there is the trail to gray butte, which is the highest peak in that range (the one with the antennas on it). we started at the day use parking lot, ran down to the bridge, and then headed right. after a couple of minutes, the trail climbs pretty steep up to the canal, and from there it's a long and steady climb on a fire road (the one you can clearly see from the day use area). it took us a little less than 30min to get to the top of that road. from there, you take the first trail on the right, and that will take you along the eastern slopes of sherwood canyon all the way to the saddle between gray butte and the range south of it (looking back, it seemed that there also is a trail on the ridge of that range, but getting there would add quite a bit of elevation to the run). from the saddle, it's fire road again all the way up to gray butte. we reached the summit after 1:18 of running from the parking area. from the summit, we took the fire road back to the saddle, and from there we took the fire road into sherwood canyon. this takes you all the way down to crooked river, and from there you'll find the trail heading south towards the park. we stopped running where the first trail to misery ridge starts climbing, and then continued up to meet some friends who where climbing on the wall south of monkey face. the run all the way to monkey face took us 2:03, with 850m/2800ft in elevation gain/loss. after resting for quite a while, we easily ran back the trail around smith rock, which is about 20min of really easy and very scenic running.
the trail run to gray butte is highly recommended, the most beautiful section is the trail on the eastern slopes of sherwood canyon. we only met three other people on the trails outside of smith rock park, and the views from the summit are really worth the trip. here's a map with a description of a slight variation (without the summit and starting at the canal, not at the parking area), and as you can see, there are many variations you can do if you want a longer or shorter run. enjoy!