HARPENDEN, an urban district in the Mid or St Albans parliamentary division of Hertfordshire, England, 25 m. N.W. by N. from London by the Midland railway, served also by a branch of the Great Northern railway. Pop. (1901) 4725. It is a favourite outlying residential district for those whose work lies in London. The church of St Nicholas is a modern reconstruction with the exception of the Perpendicular tower. In the Lawes Testimonial Laboratory there is a vast collection of samples of experimentally grown produce, annual products, ashes and soils. Sir John Bennet Lawes (d. 1900) provided an endowment of £100,000 for the perpetuation of the agricultural experiments which he inaugurated here at his seat of Rothamsted Park. The success of his association of chemistry with botany is shown by the fact that soil has been made to bear wheat without intermission for upwards of half a century without manure. The country neighbouring to Harpenden is very pleasant, including the gorse-covered Harpenden Common and the narrow well-wooded valley of the upper Lea.