Windy Pass Trail is a 6 mile moderately trafficked out and back trail located near Gallatin Gateway, Montana that features a waterfall and is rated as moderate. The trail is primarily used for hiking, camping, and birding and is accessible from June until October.
The road to the trailhead is pretty rough, but if you have a Subaru or other similar vehicle, you will do just fine. We did this hike in the evening time and the views were very nice. If you do do it in the evening, I would recommend starting before 7 because otherwise you may get caught coming back down in the dark.
My daughter and I did this hike in the summer of 2014. The most challenging part of the day was getting to the trailhead as the rocky road up took almost an hour. You may not see many folks on this hike but the views are incredible. Well worth the trouble