Martha McLean – Anza Narrows is a 40-acre regional park located along the Santa Ana River in Riverside, California, United States. The park is operated by the Riverside County Regional Park and Open-Space District (RivCo Parks). A plaque in the southwest corner of the park marks the point at which the Juan Bautista de Anza party, the first Europeans to traverse the Riverside area, crossed the river in 1774 and again in 1776.