This is up from 800,000 merchants using Square a few months ago. As co-founder Jack Dorsey explains, there are only 8 million merchants who accept credit cards in the US, so Square has already accumulated a pretty decent chunk of users.
And Square is steadily racking up marketing and retail partnerships. T-Mobile just debuted a new promotion, in which the carrier offers free Squares when its business users an upgrade to smartphone plan. And the mobile payments device is now being sold at 9,000 retail locations, which include Apple, Best Buy, Radio Shack, Target and Wal-Mart.