Weekly 5k fun run/walk (3.1 miles). Litton Trail, Sierra College, Grass Valley
https://www.meetup.com/hiking-nevada-county/events/283304964
Unguided 5k (3.1 miles, 2 loops) fun run. The Litton Trail (located across the street from Briar Patch co-op) allows leashed dogs. Suggested smartphone apps are Alltrails and Runkeeper (for tracking your time). Plenty of parking, lower lot, Sierra College. Enter Sierra College. First right into the lower lot. You will see the trailhead, on right, that runs directly down to the round-about. This is a great 5k run if you plan to run at least once per week or if you are working on your time.
Foothill Hikers - Auburn
https://www.meetup.com/Sierra-Foothill-Hikers/
Foothill Hikers welcomes new members of all ages, skill levels and interests that relish energy, camaraderie, and beautiful hikes merging one foot in front of the other. Our monthly calendar includes a variety of events mid-week and weekends covering the gamut of easy walks to more strenuous lengthy hikes all limited to a maximum of fifteen people.
Hammerin' Wheels Mountain Bike Club
https://www.meetup.com/HammerinWheelsMTBClub/
The Hammerin' Wheels are all about being active on your bicycle. We ride mostly on dirt trails but do ride paved trails/roads when necessary for trail connectivity. Due to the progression of our members over the years, most events are geared to Budding Intermediate to Advanced riders due to improved skill and fitness levels of our most active ride leaders and/or members who regularly join our rides, but occasionally have rides for novice or beginners.
El Dorado Hiking
https://www.meetup.com/el-dorado-hiking/
This is a group for hiking all around El Dorado county. Both locals and non-locals welcome. Varied days/times, varied lengths and difficulties -- from casual walks to mountains. Varied locations too, but usually on the western slope. Hikes are usually posted a few days to a week before they happen.
Trail Riders Connection - Auburn, Newcastle, Loomis, Sacramento
https://www.facebook.com/groups/716266175088148
Connecting with horse buddies in our local areas: Auburn, Newcastle, Penryn, Loomis, Granite Bay, Lincoln, Wilton, Cool, Grass Valley and Sacramento. A place to find friends for Day Rides during the week and on weekends. Members can post rides with the day and time to connect with other riders. If you are looking for a specific level of riding such as beginner or looking to ride with only 1 or 2 other people you can make that known too. Enjoy the Rides!
Placer County Group Hiking
https://www.meetup.com/Auburn-Hiking-Meetup/
Join us in exploring the wonders of the Auburn Recreation Area and lower Sierra Nevada Mt. range. Our hikes take us through incredibly beautiful regional parks, state parks, and open spaces. The group is open to adults who are physically fit, committed and show up (intermediate to strong hikers) who enjoy social hiking experiences, and meeting new people from all over Placer County.
Endurance Riding for Riders over 50
https://www.facebook.com/groups/312530175610289
This is a group for equestrian endurance competitors over 50.
Sierra Foothills Audubon Society
https://sierrafoothillsaudubon.org/
Sierra Foothills Audubon Society is headquartered in Grass Valley, California. Our membership area includes Nevada, Placer, Yuba, Sierra and El Dorado County and holds regular bird watching activities.
Auburn Area Trail Runners
https://www.facebook.com/groups/AuburnAreaTrailRunners
This is a place for anyone with a passion for running the beautiful trails in the American River Canyon and the greater Auburn, CA, area. AATR is the go-to trail running group for obstacle racers looking to branch out into trail running and racing. It also makes this a great place for any trail runners interested in trying an obstacle course race.
Gold Country Trails Council (GCTC)
http://www.goldcountrytrailscouncil.org/calendar--events.html
GCTC was founded as a non-motorized trail building and maintenance organization and provides goals and projects to sustain those founding beliefs. With over 500 active equestrian members, they hold regular day trail rides, horse camp outs and trail maintenance days in Placer and Nevada Counties.
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This is just a beginning list for those of you who wish to turn a new leaf and join groups who will help you maintain your goals of fitness, tranquility and nature watching. Use Google, Facebook, MeetUp, Twitter and other social media to find new groups who have the same trail interests you do.