Woodward & Lothrop Chairman Edwin K. Hoffman ended speculation about the department store chain's plans to enter the Baltimore market yesterday by announcing that Woodies will build a store in Baltimore's north suburbs.

The new store, the first Woodward & Lothrop unit outside the greater Washington area, will open in 1981 in the White Marsh Mall, about four miles north of the Baltimore Beltway.

The White Marsh Woodies will be the first of at least two or three units in Metropolitan Baltimore, Hoffman said.

"When you go into a new market, you don't go in with just one store," he added, saying that Woodward & Lothrop executives don't consider their Columbia and Annapolis stores part of the main Baltimore market.

Hoffman said the Washington-based chain is negotiating with several developers about possible stores in several planned shopping centers, including a Baltimore waterfront project planned by Rouse Co. of Columbia. Rouse built the Columbia mall where Woodies is located and is developing the White Marsh center.

"We've been wanting to get into Baltimore proper since long before I came here," but were unable to do so because "we weren't invited" to locate in two recently completed malls in Baltimore's prosperous north suburbs, added Hoffman.

A major reason for invading Baltimore is that Woodward & Lothrop is running out of expansion potential in Washington, he explained. The number one department store in the Washington area -- with sales of $270 million compared with an estimated $240 million for number two Hechts -- Woodies has 15 stores in the area and will open its 16th next year in Fairfax County.

Added Woodward & Lothrop President Waldo Burnside, "Every time we open a new store here, we hurt two or three of our existing stores. In Baltimore, it's all plus business."

Hoffman said the expansion into Baltimore is part of a long-range growth plan that is meant to boost Woodward & Lothrop's sales to half a billion dollars by the mid-1980s.

The company is eyeing other expansion opportunities, including the Richmond area, Hoffman said.