Both nationally and in the District of Columbia, boys have made up a vast majority of the juvenile justice population. Consequently, research, best practices, system reform efforts, and policies have been primarily based on the male population. In the past two decades, overall rates of youth involvement in the juvenile justice system have declined, yet the share of girls arrested, petitioned to court, placed on probation, and placed out of home has steadily increased. Due in part to a historical inattention to the unique drivers for girls into the juvenile justice system and the specific needs of justice-involved girls, jurisdictions around the country are seeing an increase in the rates of girls' involvement in the juvenile justice system. Over the past decade, Washington, D.C. (D.C.) has seen a significant increase in the share of girls in its juvenile justice system. This brief serves as a starting point to understand what is causing girls' increased contact with D.C.'s juvenile justice system, to highlight distinctions between girls' and boys' involvement in D.C.'s juvenile justice system, and to identify information gaps that must be addressed in order to reduce the number of system-involved girls and ensure that those girls who are already involved are receiving appropriate services and interventions. Major findings: Girls today make up a larger portion of system-involved youth than in previous years. » Over time, the proportion of 13 to 15-year-old girls entering the juvenile justice system has grown at the greatest rate. » Eighty-six percent of arrests of girls in D.C. are for non-violent, non-weapons related offenses. » In D.C., Black girls are significantly overrepresented in the juvenile justice system.