According to Mark Chirnside, conception of "Celtic" and her sisters came about in 1898 following a noticing of an opportunity to introduce a series of liners which would prioritize more on comfort rather than speed. This was accomplished in comparing the net tonnage (a measure of a ship's total enclosed space) between their two newest North Atlantic Liners; "SS Cymric", which had entered service in February 1898, and "RMS Oceanic", which was nearing completion at Belfast. "Cymric" had initially been designed as a combination passenger and livestock carrier, thus was designed with smaller engines capable of more modest speeds. When this combination proved unpopular to travelers, "Cymric" was reconfigured as a full passenger vessel. The result of this was that although she was considerably smaller than the new "Oceanic", her smaller engines and fewer boilers allowed more space for passenger accommodations. Thus, contracts were made in September 1898 for "Celtic", and her keel was laid at Harland and Wolff on 22 March 1899.