The Friday File: there are roughly 360,000 billboards in the USA. The most expensive is the largest billboard in New York’s Times Square, which measures 25,000 square feet and rents for $2.5 million/month. The largest billboard in the world is in Madrid and it’s 56,672 square feet; almost the size of a football field including the end zones! Alaska, Hawaii, Maine, and Vermont are the only states that prohibit billboards.