CrossLand Mortgage Corp., a mortgage subsidiary of First Security Bank, closed 24,483 loans worth $2.9 billion in the first quarter of 1998, a 309 percent increase in the number of loans and a 391 percent increase in dollar volume over the same period a year ago.

Company officials said they are experiencing a constant growth in sales. In 1997, the company closed $5.3 billion in loans, which was a 61 percent increase over 1996. With the $2.9 billion closed in the first quarter this year, the company already has achieved more than 50 percent of its total sales production in 1997.Christopher J. Sumner, president and chief executive officer, attributed the high financial growth in the first quarter to low interest rates, the current good housing economy and the acquisition of Harbourton/Western Sunrise Mortgage in early 1997, which added 15 new offices and 11 states and increased CrossLand's production capacity.