A reasonable portion is royalties from natural gas and oil ([source](https://www.npr.org/2022/11/10/1133554526/harvard-texas-endowment-oil-gas-billions-colleges-universities-fundraising#:~:text=According%20to%20new%20data%2C%20it,consultant%20based%20in%20Waco%2C%20Texas.)).
(They own a large amount of land).
“But how did they come to own such a large amount of land?”…
> In 1839 Texas reserved fifty leagues of public domain (221,000 acres) in good farming country northeast of Dallas to endow a state university. In 1861 it sold everything to pay for the Civil War.
> Later the state constitution of 1876 reinstated the idea of a land-based endowment for what was described as “a university of the first class.” But as so often has been the case at UT, the vision was soon compromised. The state reneged on three million acres of farmland and gave UT two million acres of desert. After forty years, the total amount in PUF was less than $1 million. Then Santa Rita No. 1 came in, and in a single year PUF grew by 445 per cent. ([source](https://www.texasmonthly.com/news-politics/texas-primer-ut-permanent-university-fund/#:~:text=Later%20the%20state%20constitution%20of,two%20million%20acres%20of%20desert.))
(Santa Rita No. 1 being an oil well ([source](https://www.tshaonline.org/handbook/entries/santa-rita-oil-well)).
EDIT: Added sources
Latest Answers