By May 1958 Koenig had completed his construction drawings and begun collaboration with factories that were capable of producing the prefabricated steelbents. The bulk of construction took place from August to November of the same year, and by January 1959 the house was officially completed.
In February 1959 Case Study House 21 was published in Arts & Architecture and was lauded as “some of the cleanest and most immaculate thinking in the development of the small contemporary house.” As was standard for all CSHP participants, the house was opened to the public for several weeks of viewing.
A year later in 1960, a photographer named Julius Shulman (himself a Case Study client) was invited to photograph the Bailey House. The photographs he took would later become iconic symbols of California Modernism. As one article for L’Uomo Vogue described, Shulman’s architectural photographs of Case Study House #21 and #22 have “an enduring resonance and iconic power. Taken on the eve of America’s involvement in Vietnam they record the last glorious moments of American post-war hegemony and self-confidence and its unquestioned belief in the benefits of progress and technology.”
Los Angeles is full of fantastic residential architecture in styles running all over from Spanish Colonial Revival to Streamline Moderne. But the modernist Case Study Houses, sponsored by Arts & Architecture and designed between the mid-1940s and mid-1960s, are both native to SoCal and particularly emblematic of the region (thanks in huge part to photographer Julius Shulman). The houses were intended to be relatively affordable, replicable houses for post-World War II family living, with an emphasis on "new materials and new techniques in house construction," as the magazine's program intro put it. Architects involved included the still-widely-remembered (Charles Eames, Richard Neutra) and the known-only-to-archinerds (JR Davidson, Thornton Abell).
A&A ended up commissioning 36 houses and apartment buildings; a couple dozen were built, and about 20 still stand in the greater Los Angeles area (there's also one in Northern California, a set near San Diego, and one in Phoenix), although some have been remodeled. Eleven were added to the National Register in 2013. Here's a guide to all the houses left to see (but keep in mind that, true to LA form, most are still private residences; the Eames and Stahl Houses—the two most famous Case Study Houses—are occasionally open to visitors).
As for the wonky house numbering, post-1962 A&A publisher David Travers writes that the explanation is "inexplicable, locked in the past."