By | September 18 2012 11:10 AM

Square, the new rising star of Silicon Valley founded and led by Twitter co-founder Jack Dorsey, closed a $200 million fundraising round on Monday that now places the start-up's value at $3.25 billion. The privately-held San Francisco based company hopes to establish itself as the go-to mobile wallet in a growing industry of digital payment systems that all seek to turn smartphones into people's primary means of transaction.