In 2020, the Esri Open Data Hub is a hidden gold mine of free GIS data. For example, it now houses over 250,000+ open data sets from 5,000+ organizations worldwide. For this reason, we have it at the top of our list of free GIS data.
In some cases, you’ll have to sift through piles of data because they’re not conveniently merged into one. Despite the extra effort, this is still arguably your best chance to find exactly what you’re looking for.
In any case, the search is convenient with a map preview of the extent and table. Alternatively, you can search by topic or location and download data in multiple GIS formats. Ultimately, there is nothing more thorough for GIS data than the Esri Open Data Hub.