"The first antenna consisted of six towers, each 300 feet high. Other towers were added later; some were made of wood and some of steel. The company abandoned the site in 1924, after other stations father north proved more efficient. The Army acquired the area in 1941 and subsequently tore down 28 of Marconi's towers"That army base referred to above is Camp Evans, a base associated with Fort Monmouth. The camp is named after Lt. Col. Paul Wesley Evans of the U.S. Signal Corps. He worked at the Belmar Station in the early 20th century. (Evans was later a signal officer at the Panama Canal Zone.)
Let's rewind. In 1912 Public Law 264 was passed. It was an early attempt by the federal government to regulate radio. It permitted the President of the United States "...in time of war or public peril or disaster may cause the closing of any station for radio communication and the removal therefrom of all radio apparatus, or may authorize the use or control of any such station or apparatus by any department of the Government, upon just compensation to the owners." More here.
In 1917 they actually did so as a part of WWI. The Navy took over 53 commercial radio stations, most of them owned by the Marconi Co. Most of them were simply shuttered. In 1919 President Wilson allowed the return of the radio properties, effective 1 March 1920. The Navy thereupon manipulated the GE buyout of the American Maroni Co. thus creating RCA. That's relevant because at RCA Armstrong used the Belmar station for the development of FM. But they had no interest in maintaining the 396 acre site in perpetuity, and abandoned it in 1924.
This is how it came to be that in 1925 it was bought by the Klu Klux Klan. That hotel, and the main Marconi building served as state headquarters for the KKK from 1925 to 1932. The property was owned by the Monmouth County Pleasure Club. The Klan's Grand Dragon Arthur H. Bell posted fliers in the area advertizing the facilities amenities: swimming, fishing, boating, golfing, tennis, and polo with the tag line "SPEND YOUR SUMMER WITH THE KLAN." More here. There was a lawsuit regarding title to parts of the property and the mortgage was foreclosed and the building changed hands in a sheriff's sale.
It was bought in 1937 by Reverend Percy Crawford who intended to build a college but didn't. The US Signal corps bought most of the property and established the Evans Signal Laboratory which was used for radar development in WWII. Even in the early 1960s the Marconi towers were still being used to receive signals from weather satellites.