In 1861 he secured the side-show privileges of the E. F. & J. Mabie Circus, then the largest show in America. He remained with this firm until 1866, when he secured similar privileges with the Yankee Robinson Circus, with which he allied himself until 1869. In the latter year he formed a co-partnership with the celebrated Dan Costello and entered upon the first of the original ventures marking as many distinct epochs in the history of the circus in America. This departure was the organization of a show which traveled by boat and stopped at all the principal lake ports of the great inland seas. This enterprise was a decided success. At that time Mr. P. T. Barnum had never been in the circus business, and Mr. Coup had not personally met this king of showmen. He keenly appreciated, however, the prestige which Mr. Barnum's name would give to a circus enterprise, and went to New York for the purpose of interesting Mr. Barnum in an enterprise of this character. This object he had no difficulty in accomplishing, and in the Spring of 1870 they put an immense show on the road, which toured the eastern States and was highly successful. The next year marked a turning point in the career of Mr. Coup and also in that of the traveling show business. He was the first man who ever called the railroad into service for the purpose of moving a circus and menagerie. This significant step was taken in opposition to the judgment of his partner, P. T. Barnum, and in the face of the doubts and objections of the leading railroad officials of the country. But Mr. Coup's faith in the results of this "rapid transportation movement" was firm, and he astonished Mr. Barnum and the entire public by the phenomenal success of this venture, which brought a rich harvest of money and reputation. The project of building a permanent amusement palace in New York came to Mr. Coup in 1874. Under his supervision, and while Mr. Barnum was in Europe, he erected, on the present site of the Madison Square Garden, the famous New York Hippodrome. His labors in this connection were so arduous that, when the great enterprise was thoroughly established, he felt obliged to take a long rest. To this end he severed his partnership with Mr. Barnum, and in 1875 took his family to Europe. Immediately following his return to America, in the spring of 1876, Mr. Coup announced that he had formed a new co-partnership with Mr. Charles Reiche, for the purpose of starting another mammoth enterprise to be known as the New York Aquarium. A large building especially designed for this purpose was erected at the corner of Thirty-fifth Street and Broadway, and was opened October 11, 1876. Into this enterprise Mr. Coup threw the energies and ambitions of a lifetime, and so long as he retained its management the great undertaking was notably successful.