There has been a market at Smithfield for over 800 years, but the current building was opened in 1868. Among the reasons for rebuilding was the provision of railway facilities: with most of the meat now arriving by train rather than on the hoof, being able to unload it on-site was a huge advantage.
The Morning Post of 3 November 1868 described the amenities:
The building for the market covers an area of 620 feet by 240 feet, and beneath the floor of this large building there is a world of railways, and sidings, and cranes, and lifts, designed to facilitate the supply of the market with its thousands of tons of meat and poultry. The Metropolitan Railway will provide access to this market for the meat-laden trains of the Great Western, Midland, Great Northern, South-Western, and Chatham and Dover Lines; and by this system of underground communication will relieve to a great extent the street traffic. ... Of the area below the market one half - the northern - belongs to the Metropolitan Railway Company, and the southern half to the Great Western, which has the right of passing over the rails of the Metropolitan.
What was coming into the market and from where? The Morning Post offered details:
The Great Northern's deliveries consist of large consignments of prime beef, which start from Aberdeen, now, in fact, one of the London abattoirs. The northern counties of Scotland add to the contributions of beef as the train proceeds southwards. In the Lothians and Lowland counties of Scotland, mutton is added by tons; and onwards in England, through the northern, midland, and home counties, the load keeps constantly increasing with beef, mutton, pork, and veal. The loads of the Great Western, smaller in aggregate quantity, are higher in relative value, including, as they do, a large proportion of the finest quality of hams and bacon from Ireland and Wiltshire. The Midland brings in a large quantity of meat and poultry from Scotland, the North of Ireland, and the midland counties. The London, Chatham, and Dover brings about 20 tons of game and poultry per week. The quantity of meat brought into London last year by railways is close upon 100,000 tons, and nearly the whole of this will, on the opening of the New Meat Market, be delivered from the railways below the level of the new building.
The railway facilities are no more. The Snow Hill tunnel which carried the railway line was closed in 1916 while the sidings beneath Smithfield lasted into the 1960s. Today, the tunnel is part of Thameslink and the space under the market has been converted into a car park.