The United States accomplished an impressive feat in 2020-21: enacting federal policy reforms that halved child poverty and uplifted low-income families amidst a global pandemic. Many of the reforms, though temporary, were unprecedented in U.S. history, representing a sea change in U.S. policy toward young children. This paper first discusses the country's chronic underinvestment in children and resulting outcomes, including new data on poverty rates among young children; the need to recognize that parental well-being (as supported by living wages, affordable housing, child care, and other infrastructure) is inextricable from the prospects of young children; and the remarkably comprehensive pandemic-era response policies, including which changes contributed most to reducing child poverty. The authors then offer five lessons, drawn from interviews with more than 30 of the extraordinary advocates and leaders who made this change happen, in the hope that they can inform future efforts to transform federal and state policy to tackle inequities across family income, race, and immigration backgrounds.