Established on March 19, 1992, the Nuveen Select Tax-Free Income Portfolio functions as a closed-ended mutual fund dedicated to fixed income investments within the United States. Jointly overseen by Nuveen Fund Advisors LLC and Nuveen Asset Management, LLC (under the Nuveen Investments Inc. umbrella), the fund strategically allocates its capital primarily to investment-grade municipal securities, targeting those rated Baa, BBB, or higher. Its financial performance is benchmarked against both the Standard & Poor's (S&P) National Municipal Bond Index and the Lipper General and Insured Unleveraged Municipal Debt Funds Average.