In the Middle Ages Warwickshire was mainly an agricultural county, but the realisation of the value of its mineral wealth, and eventually the coming of the Industrial Revolution, transformed its character. By the time of the Great Reform Act in 1832, Warwickshire had a population of approximately 337,000, of which 142,000 were in Birmingham and its suburbs; since Birmingham had been of little importance in medieval times it was not a borough, and was represented in Parliament only through Warwickshire's county members. The franchise being based on land ownership, the urban areas commanded a much smaller proportion of the votes than of the population: at the election in 1820 when Warwickshire recorded its highest turnout, only 399 of the 3,122 votes were cast in Birmingham, and a little under 300 in total from the other main towns (Warwick, Stratford-upon-Avon and Nuneaton).