Came back for the second the me in just over two weeks.  These falls are just too gorgeous to stay away from!  We hiked from the Lower Lewis campground to the middle falls while baby wearing with no issues.  Any elevation gain is gradual, and the trail is easily traveled.  There are drop offs, so if you have hiking kids, keep them close.  The middle falls are huge, but the lower falls are much more kid friendly for playing.  It was a touch over 4 miles round-trip.  The original trail was closed near the middle falls parking lot and rerouted a bit, which made it about two miles one way.  I had heard from many sources it was only three miles round trip, so I thought Id mention that.  On a weekday, the middle falls lot was empty.

Hiked from the Forest Road to the Lower Falls with two kids 3 and under.  It was crowded and busy and there were big steps down to the falls that required me to lift the kids down.  You hike in the water up to the lower falls, but once there, its a spectacular place.  One mile RT from FR to falls.

Trail conditions note: We couldn't find the trail that connected the trailhead to the river, but the Lewis River trail itself is in great shape. See below.

For a brother/sister backpacking weekend, my sister wanted "gently rising shady forest", and the Lewis River trail delivered.

* Our plan had been to leave one car at the Lower Falls Campground, but as other reports noted, there's a section of dirt road just over 1 mile south of the Lower Falls Campground that's steep and rutted. We saw numerous small cars struggling to get up the slope, and decided not to risk it.

* The trailhead location given by the WTA is for the "Speed" trailhead. On USGS maps and Gaia (see link), this point is indicated as the start of a short trail down to the Lewis River. We could not find a trail corresponding to what is shown on USGS or Gaia maps. We did find a trail at the start, but this did not correspond directly to the trail on the maps. We very quickly came to a large washout with many downed trees. We were uncomfortable crossing the washout, so tried to hike around. We couldn't pick up the trail again, so tried to use our GPS to pick up the mapped trail. We crossed over the line on the map multiple times, and could never find the mapped trail. We did see faint evidence of past hikers, so either other people have struggled like we did, or else we were seeing remnants of a very old trail. There were countless blowdowns of huge trees whose rotting trunks were challenging to cross. We eventually gave up and returned to the road.

* We walked along the road to the bridge about 1 mile south of the campground. From there we picked up the Lewis River trail, which is easy and well-traveled.

* The Lower Falls Campground page on recreation.gov indicates that most of the campsites are only available on a walk-up basis. This does not seem to be true: the campground was nearly packed, and the few empty sites were all reserved. We asked some people how they had made reservations, and they indicated that they had done so over the phone a few days before coming.

* We backtracked a bit, and found a nice campsite along the river.

* The second night we camped just above Taitnapum Falls, a bonus waterfall above Upper Falls. Some earlier campers had left an unusual campsite amenity behind: tiki torches.

Aside from the connecting trail, the Lewis River trail was an extremely pleasant, easy walk, with many nice views of the river.

July 20 2018 we hiked with two dogs, four children and two adults. I took a stroller for the puppy and toddler. We visited Lower & Middle falls. We got lost when we missed the right turn prior to trailhead and visited rear of Mount St. Helens. The trail down to lower Lewis falls has tree branches so it was necessary to watch footing. We visited during the week day which made our visit less crowded it was as beautiful as it was freezing. 

It was an extremely hot day. We arrived early AM and there was not too many people, maybe a handful but as we completed the walk it was very crowded. Most of the dogs were off leash which made it tough to control my dog who is still learning trail etiquette. The dog enjoyed himself because of all the places along the trail to stop and jump in the water. Lots of bugs, bring bug spray.