What was the number one cause of death in children in the United States in 2021?

1. Why headlines said “guns became the top killer” — a clear data pivot.

Multiple public-health reports and media analyses concluded that firearm deaths overtook motor‑vehicle crashes as the leading cause of death in children and teens in 2021, focusing on ages typically defined as 1–17 or 1–19; these findings are grounded in mortality counts and rates compiled by federal and peer-reviewed sources and amplified by advocacy groups and news outlets ^{[1] [5] [2]}. The shift reflects a marked rise in firearm fatalities from 2019–2021 coupled with continued declines in motor‑vehicle deaths over prior decades. Analysts and groups reporting this shift emphasize the statistical breakpoint in 2020–2021 and cite CDC data and specialty studies, making firearms the top external cause across those child‑teen age ranges ^{[6] [1]}.

2. The age-definition caveat that changes the answer.

Public data products use different age cutoffs; many summaries that name firearms as the top cause specify ages 1–17 or 1–19, explicitly excluding infants because infant mortality is dominated by birth‑related causes. If the question intends “children” to include infants (age 0), the top cause for that combined population is not firearms but congenital anomalies and perinatal conditions, which account for the largest share of deaths among infants and substantially affect aggregated rankings for 0–19 ^{[3] [4]}. This definitional choice is the single biggest source of apparent contradiction between sources that say “guns” and those that report accidents or congenital causes as number one.

3. What the major sources and dates show — consensus and nuance.

Analyses published in 2023 and 2024 by academic institutions, public‑health organizations, and news outlets documented the 2020–2022 trend in which firearm mortality rose sharply and became the leading cause for children/teens in the non‑infant age groups ^{[2] [6]}. Advocacy groups and research briefs quantified large percentage increases in firearm fatalities across 2011–2021, stressing public‑policy implications ^[2]. Government mortality briefs and FastStats pages continue to report cause‑specific breakdowns and emphasize age stratification; those documents serve as the underlying surveillance that produced the headline change ^{[7] [3]}.

4. Measuring differences: accidental injuries and motor vehicles still matter by subgroup.

Even where firearms are the single leading cause in aggregate for older children and teens, unintentional injuries (accidents) and motor‑vehicle crashes remain the leading cause within several narrower age bands, such as toddlers and young children (ages 1–4, 5–9) where drownings and crash injuries are prominent ^{[7] [4]}. Thus the assertion “guns are the number one killer” must be read as an aggregate statement for certain age ranges; granular age‑band analysis shows a more mixed picture and underscores how cause distribution changes dramatically with child age.

5. Limitations, data vintages, and why precision matters for policy.

Reported rankings rely on final versus provisional death counts, the ICD‑10 cause‑of‑death coding, and whether suicides and homicides by firearm are combined into a single "firearm" category. Some reports use different age brackets or focus only on 1–17 or 1–19, creating variation across analyses ^{[6] [5]}. For policymakers and clinicians the important facts are the measured rise in firearm fatalities among children/teens through 2021 and 2022 and the persistent burden of congenital and perinatal causes among infants — both of which demand different prevention strategies ^{[1] [3]}.