East of the divide, the whole landscape changes character. The road drops from the high pass and runs beside St. Mary Lake, a long, narrow expanse of deep blue water surrounded by steep peaks, and the air feels drier and windier. Forest is thinner and the mountains are more rugged. This is the rain shadow side of the park, where the clouds have dropped most of their moisture on the west, and the grasslands of the Great Plains lie just beyond.
The lake is among the park's best known and most photographed sights. It is about nine miles long, a deep trench scoured by a glacier, and its water is a vivid blue that changes with the light. A small, rocky island, Wild Goose Island, sits in the water and appears on countless postcards. Peaks rise steeply on both sides, and in early summer they are streaked with snow and waterfalls. The best views come from the road itself, where small pullouts give a view along the length of the lake.
This section is a joy to ride, but it demands attention. The road hugs the shore with a series of gentle curves, and the wind funnelling down the valley from the plains can be strong, pushing you sideways. Gusts are common in the afternoon. The surface is generally good, but expect patches of repair and the odd rock that has tumbled onto the pavement. Traffic is usually lighter than on the west side, though the pullouts and trailheads fill up in summer.
Wildlife is a regular presence. Black bears feed on berries in the slopes above the road, and bighorn sheep sometimes pick their way along the cliffs. Watch for animals crossing at dusk and dawn, and for drivers stopping suddenly to look.
The park has a few small stores and eating places on this side, but fuel is limited, so make sure the tank is full before you leave the east entrance area. The long evening light is a gift: in late June the sun does not set until nearly ten, and the peaks glow gold and pink above the water. If you can plan for an early start, you will have the lake almost to yourself.