Fed by the Illecillewaet Glacier in Glacier National Park, the river flows approximately 62 kilometres (39 mi) to the southwest,[3] where it flows into the north end of Upper Arrow Lake at Revelstoke.

[2] The river's drainage basin is 1,202 square kilometres (464 sq mi).

[3] The Illecillewaet has been of importance since the discovery in 1881 of an approach along the river to what is now known as the Rogers Pass across the Selkirk Mountains.

In 1962 the Trans-Canada Highway was constructed along the Illecillewaet west of Rogers Pass.

The watershed surrounding the river was quickly recognized to be of exceptional ecological significance, and Glacier National Park was established in the area in 1886, followed by Mount Revelstoke National Park in 1914.