the Oswestry firm of Dorsett Owen. Wrexham is on the edge of the rich Ruabon area marl beds and several brickworks sprang up in the area, among these, the most well known was Wrexham Brick and Tile and Davies Brothers in Abenbury, on the outskirts of Wrexham. Coal mining was an important industry in the area, and provided employment for large numbers of Wrexham people, however, most of the mines were situated well outside of the city. Wrexham's coalfield was part of the larger North East Wales field. A number of deep mines were constructed throughout the area including Llay, Gresford, Bersham and Johnstown. A number of new settlements were built on the edge of the city to accommodate miners at a number of the sites including Llay and Pandy (for Gresford). Other forms of mining and quarrying have taken place around Wrexham throughout its history, these include lead extracted from Minera. 20th and 21st centuries In the latter half of the 20th century, Wrexham began a period of depression: the many coal mines closed first, followed by the brickworks and other industries, and finally the steelworks (which had its own railway branch up until closure) in the 1980s. Wrexham faced an economic crisis. Many residents were anxious to sell their homes and move to areas with better employment prospects, however buyers were uninterested in an area where there was little prospect of employment. Many home-owners were caught in a negative equity trap. Wrexham was suffering from the same problems as much of Industrialised Britain and saw little investment in the 1970s. In the 1980s and 1990s, the Welsh Development Agency (WDA) intervened to improve Wrexham's situation: it funded a major dual carriageway called the A483 bypassing Wrexham city centre and connecting it with Chester and Shrewsbury, which in turn had connections with other big cities such as Manchester and Liverpool. It also funded shops and reclaimed areas environmentally damaged by the coal industry. The city centre was regenerated and attracted a growing number of high street chain stores. However, the biggest breakthrough was the Wrexham Industrial Estate, previously used in the Second World War, which became home to many manufacturing businesses including Kellogg's, JCB, Duracell and Pirelli. It is now the fifth-largest industrial estate in Europe (second in the UK) by area with over 250 businesses. There are also a number of other large industrial estates in the Wrexham