The Bentonsport boat ramp is just past the J40 bridge, and just before the restored iron truss bridge. Go past the fudge shop, buy some fudge, then stop in at the general store and museum. The boat ramp is just down the street, north of the post office. For real comfort, stay at the Mason House and see the Murphy bath tub. The Bonaparte boat ramp is off J40, next to the woolen mill and the Bonaparte Retreat restaurant.
Access is on the west side of the river.
From Bonaparte, cross the Mormon bridge west on J-40, then turn south on the river road about 3 miles. Just follow the excellent signs. The last 12 miles of my 400 mile journey began with a winter camp out overnight at the Bentonsport campground, just below this scenic overlook on J40. It was December, and it was cold.