Where the law comes from is an essential part of any legal system, one that plays a key rôle in defining it. The conventional wisdom that develops regarding systems and their sources often does not keep up with the dynamics of the systems’ development. The author feels that foreign jurists risk being misled if they believe that the United States’ legal system depends on case law, or jurisprudence in the continental sense, for most of its rules; i.e. that the United States do not have a system with written or concrete sources of law. While a sensitive comparative scholar might once have described the American system as one of conventional or customary law derived from judicial decisions, developments throughout the 20th century had the effect of mitigating this proposition, although many of those developments have not yet made their way into the foreign vision of the United States’ legal system. The author notes the proliferation of written Restatements of American Law promulgated by the American Law Institute since 1932, claiming that they enjoy an authority and derivation approaching that of a Civil Code, albeit with all the essential differences that exist between the two cases. Foreign scholars who intend to understand the law of the United States should consider the Restatements to be a primary source.