Data.gov doesn’t just catalog raw data, it also includes APIs from across government. You can browse the current catalog for APIs, but expect this listing to grow as agencies include more of their APIs as part of their data.json metadata in Project Open Data.
Data.gov CKAN API
The data.gov catalog is powered by CKAN, a powerful open source data platform that includes a robust API. Please be aware that data.gov and the data.gov CKAN API only contain metadata about datasets. This metadata includes URLs and descriptions of datasets, but it does not include the actual data within each dataset.
The base URL for the Data.gov CKAN API is:
Complete API documentation is available from CKAN.
US Government APIs
For an extensive list of government APIs and resources, check out the official microsite of the /Developer Program, a project of 18F API Engagement. You are encouraged to use that repository to suggest additions or ask questions.