Men significantly outnumber women in physics, engineering, and computer science (PECS) majors, with a recent male-to-female ratio of approximately 4:1, a stark contrast to the near parity in other science, technology, engineering, and mathematics (STEM) disciplines (1). This gender disparity in PECS carries wide-reaching implications for equity, innovation, and scientific advancement. Analyzing a near-census of over 34 million Bachelor's degrees awarded in the U.S. from 2002 to 2022, supplemented with two nationally-representative datasets, we provide the first comprehensive study of the gender gap in PECS across higher-education institutions. Institutions serving students with higher math SAT scores have made greater strides in closing PECS gender gaps--both in initial recruitment and retention--while those serving students with lower math SAT scores are increasingly struggling. Our findings highlight institutions as strategic leverage points for targeted interventions, particularly to benefit women of color who remain underrepresented even where gender balance is improving. [This paper was published in "Science" v386 n6724 2024.]