In April of that year the third battalion finally joined the Regiment at New Orleans. The entire Regiment was subsequently transferred to the Department of the Gulf. And its designation was changed by general order, first on April 4th to the 8th United States Heavy Artillery (), and then in May to the 11th United States Heavy Artillery (). On July 5th Colonel Jacob Hale Sypher of the United States Army was appointed by President Lincoln to command the Regiment. The bulk of service of this Regiment consisted of garrison and picket duty in several posts in the Department of the Gulf.
At the close of the War the Regiment was mustered out at Camp Parapet, Louisiana, on October 5, 1865 and returned to Rhode Island. On October 21st the people of Rhode Island paid tribute to the members of this command with ceremony and parade in Providence. On landing, a salute was fired by the Marine Artillery and the Regiment in column marched down South Main Street to City Hall. As the men filed into City Hall and took their stand at the tables, the band of Morris Brothers, Pell & Trowbridge's minstrels played "Tramp, Tramp, Tramp", which added to the excitement of the day. After the meal, the Regiment reformed and marched to Exchange Place, where a dress parade took place in the presence of Governor James Y. Smith, his staff, and a large crowd of citizens.
Afterwards, the Regiment breaking into columns by companies marched up Westminster Street in review before embarking for their encampment at Portsmouth Grove. A few days later, the Regiment was disbanded and the men finally returned to their homes after serving the Union cause for over two years.