They have billions of dollars under management and investments in areas as varied as coal, US Treasury bonds, and sub-Saharan Africa real estate.

No, these aren't private equity or Wall Street's biggest hedge funds.

These are nonprofit organizations serving higher education, healthcare, and the arts.

Based on second-quarter data from 2014, the finance research and data site Graypools compiled a list dominated by higher-education institutions and interspersed with healthcare funds, art-preservation societies, and financing cooperatives.

Here are the top 20 foundations and endowments in the US by gross assets, based on their regulatory filings with the IRS.

Note: Gross assets data comes from Graypools, which may "significantly inflate an organization's "size" by failing to adjust for fully-secured liabilities, such as mortgages on development real estate."