Nuveen Select Tax-Free Income Portfolio is a closed-ended fixed income mutual fund launched by Nuveen Investments Inc. The fund is co-managed by Nuveen Fund Advisors LLC and Nuveen Asset Management, LLC. It invests in the fixed income markets of United States. The fund invests in the investment-grade municipal securities rated Baa and BBB or better. It benchmarks the performance of its portfolio against the Standard & Poor's (S&P) National Municipal Bond Index and Lipper General and Insured Unleveraged Municipal Debt Funds Average. Nuveen Select Tax-Free Income Portfolio was formed on March 19, 1992 and is domiciled in the United States.