Data.gov and Science.gov provide access to information that can also be found via USA.gov, but they're better when you know you're looking for data or STEM research.
The agencies of the federal government fund a great deal of research in their subject areas. The results of these individual studies are usually published in peer-reviewed scholarly journals, which traditionally have charged high subscription fees to read. With the spread of the open access movement in the 21st century, the federal government has also begun adopting similar practices to make federally funded research available to the public without needing to pay a fee.
The first agency to do this on a large scale was the National Institutes of Health (NIH) in 2008 (following the initial announcement in 2005), and it continues to lead in the area of expanding access to research.
In 2013, the Office of Science and Technology Policy issued a memorandum, “Increasing Access to the Results of Federally Funded Scientific Research” (PDF), stating that all government agencies with research budgets of $100 million or more must develop a plan to make the results of that research (article + data) available to the public, based on the NIH's original practice. This was followed by another memorandum, "Open Data Policy-Managing Information as an Asset" (PDF) which ordered that agencies "must manage information as an asset throughout its life cycle to promote openness and interoperability." As a result, over the last several years, research and information produced or funded by federal agencies has become more and more available to the public.
Note: Unlike articles and other works published open access, which means free to read and reuse, public access works, while still free to read, are not necessarily free to reuse and may include an embargo period between being published and becoming publicly available. This embargo was later addressed by the 2022 OSTP memo (see below).
Since the 2013 memo, the residents of the White House have generally supported increasing public access to non-sensitive information and data produced by the federal government. In 2019, President Trump signed an omnibus bill that included the "Open, Public, Electronic, and Necessary (OPEN) Government Data Act," which made permanent some aspects of the 2013 data memo and established that government information should be produced as machine-readable data rather than documents. Federal agencies are now required, if they hadn't done so already, to develop an open data plan that ensures that data is in "an open format and under an open license," and those agencies will also have a Chief Data Officer to oversee the efforts.
Building on the established practices of the 2013 memo and lessons learned during the COVID-19 pandemic about the value of access to scientific research, in September 2022 the Biden administration released the OSTP memo "Ensuring Free, Immediate, and Equitable Access to Federally Funded Research" (PDF).
This document requires federal agencies that fund research and development to ensure that federally funded research publications* would be made available immediately upon publication, instead of having to wait for a 12-month embargo to pass first. It also includes guidance on access to data, establishment of persistent identifiers, and increases transparency in research funding and publication.
Federal agencies with research budgets of any amount must submit their public access plans by the end of 2024, with adoption of these plans to begin in 2025.
* "Research publications" refers to "peer-reviewed research articles or final manuscripts published in scholarly journals, and may include peer-reviewed book chapters, editorials, and peer-reviewed conference proceedings published in other scholarly outlets that result from federally funded research" ("Ensuring Free, Immediate, and Equitable Access..." p. 3).