Ridgefield — Out of 118 of Washington’s largest cities, Ridgefield was named the state’s smartest city by Career site Zippia.com. In determining how each city ranks in intelligence, Zippia examined two key factors. First, the site looked at the percentage of residents older than 25 with at least a high school diploma. Second, the site took into account the percentage of high school dropouts. According to the most recent American Community Survey, Ridgefield has a dropout rate of 0 percent, and only 1.7 percent of its residents older than 25 are without a high school diploma. Ridgefield is the only city in Clark County to make the top 10.