A changing legal industry has led a 42-year-old Lawrence law firm to merge with a Hutchinson-based practice that is looking to expand its presence in the area.

Gerald Cooley announced Thursday that he had reached a deal to merge the Lawrence law firm of Allen & Cooley with Hutchinson-based Gilliland & Hayes. The merger takes effect today. Terms of the deal were not disclosed.

Cooley said maintaining a practice with just two attorneys was becoming more difficult. Potential clients, he said, consistently are looking for a firm with a number of attorneys specializing in a wide variety of legal subjects.

“It is just not practical from an economic point of view to be a small firm anymore,” Cooley said.

Cooley’s firm, which includes attorney Randall Larkin, was a general practice but specialized in municipal law and courtroom litigation. It counted the cities of Lawrence and Eudora, plus The World Company, which owns the Journal-World, among its larger clients.

Gilliland & Hayes operates an office in Lawrence at the US Bank Tower, 900 Mass., but the merger will increase the number of attorneys in the office from three to five.

John Hampton, a Lawrence-based attorney with Gilliland & Hayes, said the company wanted to expand its Lawrence practice because of growth in the city.

“Lawrence is a growing community, and we’re picking up a lot more business up here,” Hampton said. “We felt like one of the easiest ways to expand would be to merge with a well-known, well-respected existing practice.”

The expansion increases to 27 the number of attorneys in the Gilliland & Hayes practice. The law firm has offices in Lawrence, Hutchinson, Wichita and Kansas City, Mo.

Allen & Cooley was founded by Cooley and Milton P. Allen, a son of former Kansas University basketball coach Phog Allen, in 1961.