The dominant landscape found in the park is rolling uplands and the river valley. During the retreat of the last glaciation, over 10,000 years ago, the ice melted and moved in two divisions toward the area known as the Frenchman River Valley. The northern division was higher in elevation than the southern division; consequently, the meltwater flowed south. The flow of water from the north was stopped by the southern lobe. Where the water hit the ice and ran along its margin an "ice stream" was cut into the land and became the present Frenchman River Valley. The huge amount of runoff changed the land-scape, creating coulees, buttes and creeks. The Frenchman River Valley flows south and is part of the Missouri watershed.

Water is one of the primary shapers of prairie ecosystems. Low precipitation in Grasslands National Park area influence many of the conditions that create prairies. Waterways such as the Frenchman River in the West Block and Rock Creek in the East Block add significantly to the biodiversity and are important habitats. The unique combinations of landscape and climate create niches for specially adapted plants, animals and endangered species.

Identify flora such as blue gramma grass, historically a favourite of the bison; needle-and-thread grass, whose sharp awns lend it's name; prickly pear cactus, that breathes only at night; and gumbo evening primrose, whose flowers change colour in 24 hours. The non-domination of any single species of flora and combinations of short and medium sized grasses illustrate the character of this ecosystem, and its importance in sustaining life of this planet.