North Star Mountain is located in the Cloudy Pass batholith, an intrusive formation that was formed approximately 20 million years ago, during the early Miocene.

[3][6] The history of the formation of the Cascade Mountains dates back millions of years ago to the late Eocene Epoch.

[7] During the Pleistocene period dating back over two million years ago, glaciation advancing and retreating repeatedly scoured and shaped the landscape.

[3] Uplift and faulting in combination with glaciation have been the dominant processes which have created the tall peaks and deep valleys of the North Cascades area.

As a result, the west side of the North Cascades experiences high precipitation, especially during the winter months in the form of snowfall.