We describe the design of and first results from the BErkeley Atmospheric CO₂ Observation Network, a distributed instrument of 28 CO₂ sensors stationed across and around the city of Oakland, California at ~ 2 km intervals. We evaluate the network via 4 performance parameters (cost, reliability, precision, systematic uncertainty) and find this high density technique to be sufficiently cost-effective and rigorous to inform understanding of small-scale urban emissions relevant to climate regulation.