One of the most popular hikes in Mammoth is Sherwin Lakes Trail. It is about 2.5 miles to Sherwin Lake from the trail head (5 miles round trip) with about 900 feet of elevation gain. This out and back hike can be completed in as little as 2 hours (or less) if you are an experienced hiker, but you can also extend it to a half day or full day hike if you want to take breaks to enjoy the views and/or stop for lunch at the lake. It is moderately difficult, however if you are not used to hiking at elevation it can be more strenuous.
Getting to the trail is easy, just head down Sherwin Creek Road from Old Mammoth Road. There is a pretty obvious turnoff on the right side of Sherwin Creek Rd. about 1.5ish miles from Old Mammoth Road. If the road turns to dirt (before turning), you have gone to far. At the end of the turnoff you'll see a locked gate, that is the Mammoth Motocross track, you'll turn left here and proceed to the parking lot. Alternatively, enter Sherwin Creek Trailhead into google maps and that will get you there.
The trail starts out flat and then you will quickly drop down to a creek crossing with a bridge. This is a cool spot to bring kids or dogs to just hang out if you are not interested in doing the full hike. It switches from forest shade to exposed sunshine throughout the hike, so wear your sunscreen. After you cross the bridge you'll hit a slight incline for a bit before you get to the switchback section where most of the elevation gain is located.
You will likely encounter quite a few other hikers because this is a very popular trail, so this isn't the hike for those looking for isolation. You can work up a pretty good sweat on hot days, but a full backpack of hiking gear isn't necessary in our opinion (although many people would recommend it). Make sure you have water and a little snack at a minimum.
This hike is dog friendly, so bring your pup. Once you get through the switchback section you'll hit a more open section of trail that is relatively flat. At this point you are almost there, so if you are getting tired just push through and make it to the lake. There used to be a second lake in the immediate area, but I believe it has dried up. It may still be there if you want to bushwhack and attempt to find it. It is located to the right of the main Sherwin Lake which is super easy to find.
Sherwin Lake is a great place to hang out for a couple hours. We like bring a few beers with us and hang out on the rocks by the shore. You can extend the hike if you want to go for a longer distance. If you proceed past the lake you will eventually get to Valentine Lake Trail and ultimately you'll end up at Valentine Lake. If you want to go all the way to Valentine Lake it turns this moderate hike into a more strenuous full day hike with more elevation gain and about double the milage. Sherwin Lakes trail is a great hike for experienced and beginners alike. It is best to start early in the morning (before 10am) or late afternoon (after 3pm) because the parking lot can get full.