The BlueCross BlueShield logo is visible on the side of their old building.

BlueCross BlueShield of Tennessee accounted for an estimated 86 percent of the new health plans purchased last year in Tennessee through the health exchanges under the Affordable Care Act.

The Chattanooga-based insurer said today it attracted more than 31,000 of the 36,000 Tennesseans who enrolled by the end of December.

Of the total number of BlueCross enrollees, the biggest share was in the Nashville and Knoxville areas.

The estimated enrollment figures represent the period of Oct. 1 through Dec. 28 dates for which the U.S. Department of Health & Human Services reported that 36,250 Tennesseans had signed up for a marketplace plan. Nationally, enrollees for the same period stood at 2.2 million Americans, according to HHS. Enrollment for the Marketplace continues through March 31.

"We're proud to be the insurer of choice on the Marketplace in Tennessee," said Henry Smith, senior vice president and chief marketing officer for BlueCross. "We worked hard to provide the most plan options of any carrier, with multiple networks and a range of pricing to meet the needs of individuals seeking coverage."

In Tennessee, four health insurance companies will offer plans on the exchanges -- BlueCross BlueShield of Tennessee, Cigna Healthcare, Coventry Health & Life and Community Health Alliance. Chattanooga-based BlueCross is the only insurer to offer plans in all 95 Tennessee counties.