Halliday and his brothers achieved substantial business success following the Civil War through a variety of businesses and investments. One commentator has stated that by the 1880s the Halliday family was among the most powerful in the region, and Halliday was the significant figure in the family. Halliday the driving force behind the firm of Halliday Bros in Cairo had four brothers, the brothers together operated as members of the firm Halliday Bros. The brother's character in business and personal life has been noted in many writings, publications, and books, one such book A History of the City of Cairo Illinois by John M. Lansden speaks of the brothers: There were five of them, a somewhat exceptional number: William P. Halliday, Samuel B. Halliday, Edwin W. Halliday, Henry L. Halliday, and Thomas W. Halliday. Of them all, I may be permitted to say that while they all differed from each other, they all exhibited features of character and conduct that would have given them prominence anywhere in the business world. No doubt in some one or two important respects, each one excelled the others. This was shown in those matters and things to which they gave their chief attention. Speaking of them and their families, so well represented here with us and elsewhere, it can be said that they have always stood for better things, not with assumption or pharisaically, but openly and firmly. They pushed their business enterprises with diligence, and had there been more of such men it would have been better for the city and for them also, I have no doubt. The Halliday business empire following the Civil War comprised numerous businesses in Cairo, cotton lands in Arkansas, a hotel in
Memphis, Tennessee, furniture companies in Memphis and New Orleans, coal mines in southern Illinois, salt wells in southern Illinois and Indiana, numerous large farms, and many other investments. Halliday and his brothers dealt heavily in flour following the Civil War. In order to keep updated on their daily business activities Halliday and his brothers installed private telegraph lines between their residences and their business offices. In the early 1870s Halliday held the public office of city councilman for the city of Cairo Illinois, for the city at large ward with Daniel Hurd. On March 5, 1867, Halliday,
David J. Baker Jr., Alfred B. Safford, Daniel Hurd, and George D. Williamson were granted permission by the Illinois legislature to incorporate The Valley Iron Company. The capital stock of the company was $200,000 and the company headquarters were in Cairo, Illinois. The company's purpose was to mine and manufacture iron and other metals, with the stated purpose of supplying railroads. Also at this time, Halliday, Hurd, Safford, and others served on the transportation committee of the
Illinois Central Railroad. During the Civil War Halliday was associated with the
Mobile and Ohio Railroad through the railroad's use of his wharf boats. After the war, Halliday became a major investor in the railroad along with
William Butler Duncan I, Charles Walsh, and Charles Edward Tracy. Halliday's investments centered around the railroad's expansion to Cairo in the late 1870s. On April 22, 1874, the shareholders of the Mobile and Ohio Railroad elected Halliday to the board of directors. As Halliday's business interests grew, he began investing in businesses that supported his railroad and steamboat businesses, primarily coal mines. Halliday purchased his first coal mine in St. John, Illinois, to supply his steamships and coal depots. Due to the success of the coal mines, Halliday began to purchase property in the area to search for oil. He was unsuccessful in locating oil deposits but did find one of the most productive salt mines in the region. Haliiday's brother-in-law, Marion Wright, ran and oversaw the Halliday coal and salt mines. Although Halliday had originally invested in the Cairo and Vincennes Railway in 1865, it was not completed and incorporated until July 9, 1880. In the 15 years in between, Halliday was able to attract many influential and important investors to the project. Banking tycoon,
J. P. Morgan served as president and as a director of the railroad with Halliday. In 1869, Halliday spent eight weeks in New York City with co-investors Burnside, Hurd, and Raum trying to get investment for the Cairo and Vinncennes Railway project. During the trip, Halliday was able to gain the support and investment of the United States railroad construction company. ==William P. Halliday and the town of Hallidayboro Illinois==