Most people see the Gateway Arch from the Missouri side — from the riverfront, from the park, from below. The view that most people miss is from across the river, from the Illinois side, where the Malcolm W. Martin Memorial Park gives you something completely different: the Arch above the St. Louis skyline, the full silhouette, with the Mississippi in the foreground.
The Mississippi River Overlook is a five-tiered concrete and steel observation structure, 40 feet tall at its highest point, in East St. Louis across from the Arch and the downtown waterfront. The lighted stainless steel railings make it usable at night as well as during the day. It's handicap-accessible and open seven days a week from 7 AM to 10 PM.
What you get from the top platform is a genuinely postcard view — the kind of photograph the city itself can't quite capture because you need distance from the Arch to see it properly. The Gateway Geyser is visible from here too, a water feature that shoots 630 feet when active, matching the Arch's height.
The park is quiet, especially on weekdays. East St. Louis doesn't attract the tourist traffic that the Missouri side does, which means the overlook often has the view to yourself. The reflection of the Arch in the river at the right time of day is the image I came back with. It requires crossing the river, which most St. Louis visitors don't do, and that's exactly the reason to do it.