Lawson’s mature landscape style, expressionist in execution, is revealed in May in the Mountains (1919). May in the Mountains, a riotous celebration of spring, has the tactile pigments, frantic bursts of color, raised horizon, and psychological intensity that recall the paintings of Vincent Van Gogh. Lawson applied multiple layers of paint, at times rubbing them into the layer beneath, and forming a built-up network of colors—yellow, white, and grass-green; some hues are blended, some placed side by side in short strokes. He juxtaposed warm and cool shades and bathed the scene in a form-diffusing light that blurred the middle ground under a wealth of blossoms.
The massive and craggy mountains in the background suggest Canada rather than New England. The scene is possibly a composite created from memories of Cornish, New Hampshire, where Lawson and his family spent the summer of 1919, and Nova Scotia, where the artist had an exhibition that year.
One of the few paintings dated by the artist, May in the Mountains was one of Duncan Phillips's favorite oil paintings. Phillips delighted in the painting, describing it around 1924 as "an orchard of flowering trees in a mountain valley where the ecstasy is like the rhythm of the morning stars when they sang together."