Only a day after it began, a blaze that started outside the hilly town of Paradise in California had grown to nearly 362 square kilometers and destroyed more than 6,700 structures, almost all of them homes, making it California’s most destructive wildfire since record-keeping began. Most of its buildings are in ruin. Entire neighborhoods are leveled. The business district is destroyed. In a single day, this Sierra Nevada foothill town founded in the 1800s was largely incinerated by flames that moved so fast there was nothing firefighters could do.