The National Child Traumatic Stress Network (NCTSN) is a federally funded child mental health service initiative designed to raise the standard of care and increase access to evidence-based services for traumatized children and their families across the United States. As part of the quality improvement goal, a Core Data Set (CDS) was established to standardize data collection and examine treatment outcomes across participating centers. This paper describes baseline demographic characteristics, prevalence of trauma exposure, and service use for children and adolescents served by a broad range of NCTSN service delivery centers. Data were collected from children 0–18 years (52% girls, 82% were 6–18 years old) who reported exposure to at least one trauma and who received trauma-related services (n = 11,104). Approximately half the sample was White; more than three quarters reported exposure to multiple types of trauma. Sixty-three percent were eligible for state- or federally funded insurance. The two most commonly reported traumatic events were traumatic loss/separation/bereavement and domestic violence. Number and type of trauma exposure varied by gender and age. Type and number of services utilized prior to entering an NCTSN center varied by number of trauma exposures. Systematically assessing children's trauma exposure provides clinically useful information, particularly for those exposed to multiple types of traumatic events. Identifying subgroups, and markers of risk for trauma-related sequelae, may inform policies, programs, and best practices to meet specific needs of children and families. Future research may clarify high-risk trauma profiles for coordinated utilization of systems of care.