Roughly one in four newspapers in the United States has closed since 2004, and many that managed to survive have been cut to the bone. Now, more than 260 dailies will be controlled by the same company.

Shareholders voted on Thursday to approve a deal that would join the two largest newspaper chains in the United States, all but guaranteeing the creation of a newspaper colossus that is likely to result in thousands of layoffs.

The combination of GateHouse Media and Gannett — already the two largest newspaper owners in the country, by both number of papers and print circulation, according to researchers at the University of North Carolina — means that more than 550 newspapers, 300 of them weeklies, will have the same owner.

The merger is expected to reach formal completion on Tuesday, the companies said in a statement on Thursday. Shareholders with stakes in both companies voted in favor.