Case Study House No. 21, designed by architect Pierre Koenig, is part of the Case Study House Program initiated by Arts & Architecture magazine in the 1940s. Completed in 1960, it is located in Los Angeles, California and showcases modernist design principles, emphasizing open spaces and integration with the surrounding landscape. The house features a steel frame and large glass walls, allowing for abundant natural light and stunning views of the city. Its innovative use of materials and minimalist aesthetic exemplifies mid-century modern architecture, making it a significant example of the era's design philosophy.