Is there an easy method for determining river mile?

I would like to determine the river mile of 25 sites along the Ohio River (USA). I understand that there is an ArcGIS tool for measuring the distance between two points, but I am not sure how accurate this method would be for a river that stretches nearly 1000 miles. Is there an interactive map or GIS data layer that will show river mile by clicking on any point of the river?

ArcGIS

Rivers

Maps

Hydrology

Cartography

26th Sep, 2015

Daniel Pierre

Antea Group

Working more in Europe and in Africa, I do not know where to find the geographical data necessary for it (I guess you have). However, for the cases where you would have no geographical data allowing to realize it, you can create them. Under ArGis for example, you just have to create a "shapefile" and declare the object as polylignes "M" then to size the upstream and the downstream of the river, that is define the starting point "Miles" = 0 and the point to arrive "Miles" = XX miles