Marsden Hartley painted Mountain Lake—Autumn around 1910, on one of his first trips to Maine. In the painting, Hartley uses bright, fauve-like color reminiscent of the work of Henri Matisse and heavily textured brushstrokes, similar to Swiss impressionist Giovanni Segantini, to provide solidity and weight to the scene, which was typical of his work during those years. In addition, Hartley dispensed with the framing devices of his earlier Maine mountain series, thus attaining an expressive, lively effect.
The inscription on the back of the painting indicates that Hartley gave it to his friend and fellow artist Rockwell Kent in 1912. The two had become friends while exhibiting together in the 1911 Independent Exhibition at New York's Gallery of the Society of Beaux-Arts Architects. Kent later gave the painting to Duncan Phillips in appreciation for the financial assistance he was receiving from Phillips at the time. Phillips 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, with its “tapestried” colors and “Ryder-like cloud formations” became one of Phillips’s favorite pictures.