Wildfires classified as being caused by smoking materials has undergone a steady decline over the past three decades that, until now, was not fully understood. Statistical models developed by researchers at the Forest Service and the National Institute of Standards and Technology found that a small but statistically significant share was due to the decline in adult smoking rates. But nearly one-quarter of the decline was due to the introduction of self-extinguishing cigarettes, now required in all 50 states. The size of the effect of less fire-prone cigarettes was unexpected, given that the technology was designed to reduce smoking fatalities in residences. Finally, wildfire investigation training emerged as the single largest reason for the decline in fires attributable to smoking materials. The improved accuracy in fire classification means that wildfire prevention specialists can better target their messages at the causes most likely to yield the biggest gains in unwanted fires on our public and private lands.