After mustering out later in 1865, Grubb returned to Burlington and established himself as a prominent iron manufacturer, taking over the family's business that went back to his great great grandfather, Peter Grubb Jr. He was president of the Lebanon Valley Furnace Company from 1867 until about 1911. In 1868, he married Elizabeth Wadsworth Van Rensselaer (1848–1886), daughter of an important family in the area. Together they had one daughter. He was elected to the Burlington City Council where he served as its president for two years. He and his wife found time to travel extensively in Europe and accompanied Baron de Lesseps through the Suez Canal. His 1869 account of the canal and its technical aspects was the first such article to be published in the United States. In 1872, he had fellow veteran Frank Furness design a house on the river, still known as "Grubb Cottage". In 1874, he built a estate at Edgewater Park Township, New Jersey, called "Grassmere", where he annually entertained the survivors of the 23rd regiment.