Economic ventures of the family were diverse: interest in Treasure Hill silver mines in Nevada, farmland in the Kankakee area of northern Indiana near Chicago, turnpike construction, railroad financing (Thomas was one of the original stockholders of the Ohio and Mississippi railroad, later known as the Baltimore and Ohio or B&O Railroad), packet boats and steamboats. The Gaffs owned at least 16 steamboats, among them the Diana, Mary Pell, Eclipse, J.W.Gaff, and the Forest Queen. The Forest Queen was commandeered by the Federal Government and successfully ran the blockade at Vicksburg, during the Civil War. The Forest Queen was later burned to the water at St. Louis by Confederate forces. For several years, the Gaffs were in litigation with the Government but were never able to recoup their losses.
Thomas Gaff was among the founders of the Aurora Gas Light and Coke Company, which began supplying gas for home lighting in 1860 and for street lighting by 1874 or 1875. He was a founder of the First National Bank in 1856, Thomas being its first president and serving in that position until his death in 1884. Additionally, the first telephone in Aurora connected a family business in Cincinnati to the T. and J. W. Gaff Distillery in 1869. James W. and Thomas were partners in the Aurora Home Insurance Company in about 1860. The Gaffs were instrumental in getting Stedman’s foundry moved from Rising Sun to Aurora.
By 1873, the Gaffs had established the Crescent Brewery at the foot of Market Street on the Ohio River. This had been preceded by other breweries of different names, also owned by the Gaffs. Products of the brewery were supposed of excellent quality and some were exported to Germany.
The Gaffs, or more particularly James, may have been instrumental in getting the Fleischmann family to come to America and experiment with their yeast for brewing. After many unsuccessful experiments, the Fleischmanns reverted to their original yeast formula and set up a bread-making booth at the Philadelphia Centennial Exposition in 1876. This was a very popular and successful venture, thus making Fleischmann’s yeast very well known. In addition to these ventures, some of the Fleischmanns came to Cincinnati and were partners with J. W. Gaff in a distillery.