On the eastbank from the current Lansing Center promenade (from where the first two pictures were taken) to the Shiawassee Street Bridge, to the north. So two blocks, three if you include the existing promenade, itself. On the westbank two blocks to the same bridge.
All of it, though, is formally part of the Lansing River Trail system, which depending on the geography, switches between riverside asphalt pathways and boardwalks for over thirteen miles through the city.
lansingrivertrail.org
The map is actually slightly incorrect. The northern end actually extends a little further north, and technically, where the trail hits the East Lansing city border is where it ends (the trail through MSU is of their own making), but it's fairly accurate.