Mobile payments company Square is hosting a grand opening Tuesday night for its office in the Cortex innovation district in the Central West End, opening its doors to St. Louis entrepreneurs and business leaders.

Square was co-founded in 2009 by two St. Louis natives, CEO Jack Dorsey and Jim McKelvey, owner of the Third Degree Glass Factory on Delmar Boulevard. McKelvey turned to his friend Dorsey, a co-founder of Twitter, to help develop an easier way to process credit card payments for his glass business.

"Jack and I didn't know what we had," said McKelvey, who greeted visitors at Square's open house. "What we knew very clearly is that I as a small merchant had a problem accepting a payment. We didn't know that millions of people had the same problem."

Square, which went public last November, has grown its services beyond its credit card readers to include iPad point-of-sale stands and access to capital for small businesses.