Lewis's other works include:
- *With Rope and Gun in the Rockies* (1911), a travelogue of her experiences in the Rocky Mountains
- *The Wildcat* (1912), a novel set in the American West
- *The River Ranch* (1914), a novel about a young woman who inherits a ranch in Wyoming
- *The Wolf Hunters* (1915), a novel about a group of hunters who track down a pack of wolves
- *The House in the Desert* (1917), a novel about a young woman who moves to the desert to escape her past
- *The Woman Who Dared* (1918), a biography of the journalist Nellie Bly
- *The Yellow House Mystery* (1919), a mystery novel
- *The Green Goddess* (1920), a novel about a young woman who is kidnapped by a Hindu priest
- *The Forbidden Trail* (1921), a novel about a young woman who travels to India in search of her missing brother
- *The Mystery of the Golden Keys* (1922), a mystery novel
- *The Secret of the Tower Room* (1923), a mystery novel
- *The Phantom Clue* (1924), a mystery novel
- *The Riddle of the Locked Room* (1925), a mystery novel
- *The Clue of the Broken Vase* (1926), a mystery novel
- *The Shadow of the Black Rose* (1927), a mystery novel
- *The Case of the Crimson Kiss* (1928), a mystery novel
- *The Sign of the Seven Sins* (1929), a mystery novel
- *The Puzzle of the Silver Spoons* (1930), a mystery novel
- *The Secret of the Locked Chest* (1931), a mystery novel
- *The Mystery of the Hidden Room* (1932), a mystery novel
- *The Clue of the Twisted Candle* (1933), a mystery novel
- *The Shadow on the Wall* (1934), a mystery novel
- *The Case of the Missing Heiress* (1935), a mystery novel
- *The Phantom's Secret* (1936), a mystery novel
- *The Clue of the Scarlet Thread* (1937), a mystery novel
- *The Mystery of the Hidden Treasure* (1938), a mystery novel
- *The Case of the Poisoned Chocolates* (1939), a mystery novel
- *Rosa Ponselle* (1940), a biography of the opera singer Rosa Ponselle