James Niehues sat down in his basement studio and took out his no.2 brush. With patient vertical strokes, he added the finishing touches to his latest canvas, Mad River Glen, a bowl-shaped valley, woven with ski trails, that sinks 2,000 vertical feet into Vermont’s Green Mountain Range. Autumn light filtered through the lonely high window, beyond which lay Denver, Colorado. Niehues didn’t pay it much attention. He rarely looks at real mountains when he’s painting.

There are probably tens of thousands of trees on the slopes of Mad River Glen, and Niehues has hand-painted every single one. He discriminates between conifers and deciduous trees, because skiers legitimately care about the difference. Trees at high altitudes are blue, caught in shade or lost in the ozone. Lower slopes are picked out in forest greens and pale sunrise gold. His mountains are usually frozen in a particular light, what American skiers call ‘Bluebird’, when the sun hits an acute angle and shadows catch on the snow, with a cloudless sky so blue it hurts the retinas.

On the walls of the studio hang other mountains. Boreal. Big Sky. Crested Butte. Kicking Horse. Deogyusan in South Korea. Well-skied slopes from Oregon to Maine, Idaho to North Carolina. Powder trails in New Zealand, Australia, Serbia, Chile and Japan. Niehues has painted them all. For over 30 years, he’s been almost the sole practitioner in a very niche artistic field: illustrated ski slope maps. His style has become so ubiquitous that it’s almost invisible; most skiers don’t even recognize it.