Dave from Kirkwood on 5/3/2021 7:29:14 PM:
I think I see what you are seeing. If you have just the right zoom setting on google maps, there is a dashed line across the river going NW from Howell Island to the Katy trail. That is NOT a trail/bridge. Looking at the satellite view, you can more clearly see that there is nothing there at the dashed line (besides muddy water).
Having said that, one can access Howell Island from the Chesterfield side, but only when the flow in the channel between the island and the mainland is low. I have parked at the conservation area parking lot (off Eatherton Road) and biked across and around Howell Island once. It was nice, but quite rough compared to the Katie (more of a hiking or hunting access trail).