The California Roadkill Observation System (CROS) was launched in August 2009 as a novel US-state scale wildlife-vehicle conflict (WVC) reporting system. Since its inception, CROS has collected over 212,800 observations making it the largest WVC reporting system in the US. WVC observations have come from several sources, including amateur observers; state, federal, and local agencies; private entities; and highway patrol officers. Spatial accuracy of observations is <13m (median error) and species identification is >97% correct, with no difference between professional and amateur observers. Multiple uses have been made of the data: 1) Planning dozens of wildlife fencing/crossing projects throughout the state; 2) To model habitat suitability and species distributions; 3) To locate high-density and statistically-significant clusters of WVC (hotspots); and 4) To estimate the economic costs of these crashes and compare to costs of building fencing. Because of its longevity and size, CROS has served as a global standard for other more recent large-extent systems. It also seems to be motivating state policy and expenditures, evidenced by citation of the system in legislative language. There are many lessons learned from developing, managing and using a system like this, not least of which is the near-impossibility of getting funding.