The National Institutes of Health (NIH) has had a Public Access policy in effect since 2008, enabling NIH-funded research to be made openly available to the world via PubMed Central. This very successful policy inspired a broader implementation of Public Access policies across the federal government.
On February 22, 2013, the Office of Science and Technology Policy issued a memo to Federal agencies funding over $100 million in research and development, to develop a plan to support increased public access to the results of research funded by the Federal Government. Since that date, many agencies have issued Public Access Policies for anyone receiving agency research funding. These policies address not only traditional research publication in the form of a journal article; many now also madate data amangement plans as a requirement for all funded research grants.
The U.S. Federal government maintains a page with the details of each agency's plan and effective date - including those that are already active like NIH, and other agencies who are intending to launch their policies in the future. Since this infomration will change over time, we are not reproducing them here; we are relying on the page below to keep us all updated.