Just rode the entire trail with my daughter, Oct 16 and 17. We started in Council Grove and rode East. We were on hardtail mountain bikes.
From Council Grove to Osage City the trail is in absolutely perfect condition. It's wide, (10 -12 feet),smooth, hard and fast. Many times I thought I was riding on pavement. I even locked out my front fork because I didn't need it. All the bridges are new. Guys with road bikes, have fun you'll fly. Congratulation to the Parks Dept for all their work, this portion is as good as it could be.
Then you hit Osage city. Oh boy, time to unlock the fork. From there to Vasser it's pretty rough. You come to HW 31 on the East side of Osage City and your looking at a overgrown weed patch along the junkyard. The sign said it's the trail so we went. There is still a pretty good gravel base so just pick your line and go. Then heading east go through the parking lot at the grain elevator and the trail stops at 5th st. There is no signage. We just kept going straight because there were no " private property" signs. It's all grass no path. Then at 6th street you have to detour to the south on Lakin Street. Ride Lakin east and turn left at Sonic then North back to the trail. It's a very short detour, no big deal.
From here to Vasser, again it's hit and miss. Some sections are OK and others are pretty rough. We were lucky because it hadn't rained in a while and trail was bone dry. There are lots of sections that are just dirt that would very tough if it was muddy. There was one section just as you go over the bridge at HW 75 that was very fine deep loss dirt. It was dry and we still had to ride in the weeds on the shoulder where the ground was hard to get through. If that was muddy, forget about it.
From Vasser east the trail goes back to the " improved" condition.
We got off at HW 368 and went north and camped at Pomona State Park.
Very nice park with facilities. There is also a good restaurant on the left by the motel and golf course. Open all day.
Back on the trail in the morning and through the only tunnel on the trail under HW 268. Like I said from here on the trail is back to the " improved" condition. Not quite as nice as from Council Grove to Osage city but still very good. Just a few more bumps and chatter.
Lot of dead trees down but that was because of the bad wind storm we had the night before. We weren't in a big hurry so we just cleared them ourselves.
I did run into a parks truck doing maintenance and got a lot of good info.
That bad portion through Osage City is waiting on some bonds for funding and that eventually the trail is going to have bathroom facilities, water and mile markers just like the Katy. They already have mile markers from Ottawa to Osawatomie.
Anyway heading east we ran into a big detour at Iowa rd. The trail is closed there or should I say non existent. You have to take the detour which is well marked and takes you out on the country gravel roads. The roads aren't bad. It's not the " big" gravel you think of when you hear " gravel road" but fine crushed gravel very similar to what's on the trail. The detour is about 3.5 miles and you get back on the trail at Louisiana Ter. At this point your about a mile West of Ottawa.
From Ottawa to Osawatomie the trail is in great shape but some of the bridges haven't been replace or updated yet. There are about four or five with no railings. Most aren't very high but one is about 30'. I just mention this in case someone is taking some young kids. On that big one I don't know why they couldn't a least put in a couple posts and at least string some cables just so there is some protection.
The trail now does go all the way to the Karl E Cole baseball complexe and ends there in nice big parking lot.
I hope this update was useful. Reading older posts when I was researching this trip I was expecting the worse but i can tell you that we had a great time and the trail is in great shape with that one section and detour as the exceptions.

Carl Spahn with daughter Madison
Kansas City, Mo.

Rode the trail starting in Osawatamie. Trail was in great shape, though some parts had a lot of leaf coverage. Despite this, no issues with surfaces or slippage. Such a peaceful trail to ride. And it flows super fast.

40 miles of outstanding trail. Rapid improvement of Flint Hills nature trail due to its designation as a state park. From Osage city to Allen the trail is 20 feet wide of crushed lime stone. From Allen to Council Grove 15 feet wide crushed lime stone with rock formations and fossils on both sides. Bathrooms,food, and water in Osage city, Allen, and Council Grove. Camping available in multiple sites along the way.

Super nice trail with crushed stone. Many on/off access points along the way. It is not busy at all. There were a few walkers & runners. There are not many roadways to cross either

Well used. I have run on the majority of this trail. Would be fine for Cycling with a hybrid, Gravel or mountain bike. The Levee portions of this trail has nice views of the river.

Path is 3/4th crushed stone when you do come across paved sections it makes you thankful. There are multiple points of entry and exit along the road. Path isn’t very scenic but still a worth while trail to explore.

Today we rode the Flint Hills Trail from Osawatomie to Ottawa and back. We had a great time and this trail is highly recommended! The trail is a "Rails to Trails" route that follows the Marais des Cygnes river, so it is predominately flat. The gravel surface is packed very light chip, so almost any type of bike will work (we rode gravel bikes). In a few places, the recent heavy rains washed away the light chip top coat and exposed the more coarse RR bed gravel below, but it is not a problem. We did not see any of the thorns etc. mentioned above in posts from previous years. The trail head is a little hard to find, and Google maps did not help. If you find the Osawatomie elementary school and then proceed down that same road about 3/4 mile further, the trail head (with some parking) is on your right. Leaving on the trail from Osawatomie, the first 6 miles are completely shaded by trees arching over the trail. After that the trail is about 1/2 shaded and 1/2 open meadows - so this is a great trail for warm summer days (and should be beautiful in the fall). There are many bridges, views of the river and wide open farmland to see along the way. Today, at 9 miles in, there was about 200 yd where water covered the trail from the big overnight thunderstorms, but this is not normal. There are no drinking water stops along the way - so bring at least 2 good sized bottles per person. There are however farm houses all along, so if you really needed help in an emergency, it is not far away. Ottawa is about 18 miles from Osawatomie and you will know that you are close when you pass under the I-35 bridge (about 2 miles to go). If you want lunch, turn left off the trail at 7th street (it is well marked), go ~1 mile south on 7th and you will hit Main street. Subway is 2 blocks to your left (9th street) on Main, or you can go to downtown and have a variety of food choices. We had a really nice ride today and hope that you can ride this trail soon too!

This is a lovely trail. I camped at Vassar Lake for a few nights and rode sections out and back each day between Council Grove and Osawatomie. Trail conditions were great for a gravel, mountain or touring bike. There are a few rough bridges, and a few patches of ballast or deep sand, but nothing that will ruin your day. My first morning I followed a coyote following a turkey for the better part of a mile. In Ottawa you can also connect to the Prairie Spirit trail, which is also nice.

I walked a section from Anderson ave to Manhattan ave S on a very windy day. Most of this section was along the river and lined with trees so the wind was not bad. Great walk. A few joggers and cyclists were out. A little city and country mixed in.The section starting at Pecan Circle was supposed to be the beginning of a scaled section of the solar system. Mercury was marked and the next marker was Saturn.????? I was disappointed but maybe it was never finished? Great trail to walk or bike along. Thanks!