One of North Carolina's largest law firms is merging with a national giant, the firms announced Wednesday.

Helms Mulliss & Wicker, which has more than 145 lawyers in Charlotte, Raleigh and Wilmington, is combining with McGuireWoods, a Richmond, Va.-based firm with 750 attorneys worldwide that opened in Charlotte in 1998.

When the merger takes effect March 31, the combined firm will be known as McGuireWoods and will have about 160 lawyers in Charlotte.

The merger is a result of clients' changing needs, McGuireWoods Chairman Richard Cullen said in a press release.

"We need to match our capabilities and geographic reach to meet those needs," he said.

Helms Mulliss' chairman, Peter J. Covington, will become vice chairman of McGuireWoods. Scott Vaughn, Helms Mulliss' finance group leader, will become managing partner of McGuireWoods' Charlotte office.