Chances are that ATM you just tapped at the local convenience store for $100 was owned by Cardtronics USA Inc.

The Houston-based retail ATM operator and owner, a subsidiary of Cardtronics Inc., has massively increased its ATM fleet by acquiring all assets of ATM Networks Inc.

ATM Network provides machines to more than 6,000 independent merchants nationwide. In some cases, Cardtronics owns the machines; in other cases, merchants own them. The purchase adds 21,300 merchant-owned ATMs to Cardtronics’s portfolio. Cardtronics owns 39,900 machines, including those in the ATM Network transactions, for a total of 61,200 ATMs under its control.

Terms of the transaction were not disclosed.

Cardtronics said it expects the acquisition to add annualized revenue of $7 to $9 million, or about $1,080 per machine per merchant-client. Assets acquired includes ATM Network’s Minnesota-based head office, merchant contracts, customer relationships, online store and web properties.

Cardtronics said it expects ATM Network’s management team and employees to join its staff. Phil Rock, founder, president and chief executive of ATM Network, will assume the day-to-day leadership of Cardtronics’s merchant ATM business, the company said.

“This year, we’ve strengthened our commitment to the merchant line of business by acquiring the assets of the premier merchant own-and-load operation in the market today, ATM Network,” said Cardtronics’s Steve Rathgaber, chief executive, in a statement.