The vibrant landscape scene, Mountain Lake—Autumn, was executed during Hartley's earliest painting trips to Maine. His interest in the vast mountainous landscape of his native state is captured within this fall scene. Mountain Lake—Autumn reveals Hartley's style of around 1910, when his landscapes had bright, fauve-like color reminiscent of Matisse and heavily textured brushstrokes that provide solidity and weight to the scene. In Mountain Lake—Autumn, Hartley applies short, closely-knit strokes that enabled him to use color to its fullest potential. Here, he abandons framing devices such as the vertical trees of his earlier Maine mountain series, thus attaining an expressive, lively effect.
The inscription on Mountain Lake—Autumn, “For Rockwell from Marsden Hartley,” indicates that Hartley gave it to fellow painter Rockwell Kent in 1912. The two had become friends while exhibiting together in the 1911 Independent Exhibition in New York. Kent later gave the painting to Duncan Phillips, who wrote to Kent: "The Hartley is so fine a picture that I hesitate to accept it but the reason you give is a good one, namely that in our Gallery many people will enjoy it to the artist's benefit and to our mutual satisfaction." Mountain Lake—Autumn was one of Phillips’s favorite works, depicting "mountain sides...tapestried to the top with autumnal colors and rimmed with luminous Ryder-like cloud formations."