27 May 1933: FDR signs the Securities Act

On May 27, 1933 President Roosevelt signed the Securities Act, requiring companies selling stock to the public to register with the government and disclose audited financial information. Before it, state laws had done little to stop fraud. The registration statement now known as the S-1 traces back to it, and a year later the SEC was created to enforce it. Disclosure became the backbone of American markets.

The lesson: Disclosure only protects investors who actually read it; the prospectus is homework, not decoration.