CoStar's researchers drove city streets photographing office buildings and phoning landlords to ask what space was empty. Nobody else bothered to collect it all. Andrew Florance started the company in 1987 to build that record of commercial real estate, and brokers came to depend on it. When it filed to go public in 1998, it was still called Realty Information Group, a Bethesda firm selling data to brokers, owners and lenders.

Knocking on Every Door

Florance founded the company with backing from Michael Klein, who became chairman. Commercial real estate ran on scattered, private knowledge: who owned a building, what rent it asked, which floors stood vacant. The company paid researchers to gather it street by street and kept it current. Brokers paid subscriptions to search it. The bet was that one complete database, expensive to build and hard to copy, would become the industry's standard.

A Nine-Dollar Start

The company priced its offering at $9 a share in July 1998 and listed on Nasdaq, later trading as CoStar Group under CSGP. It spent the next decades buying rivals and moving into rentals and homes, adding LoopNet, Apartments.com and Homes.com. It became one of the largest real estate data companies in the world. CoStar remains a public company on Nasdaq.

Cover: The Evening Star, second plate, Henri Fantin-Latour. Art Institute of Chicago, public domain. Chosen for the evening star (CoStar).