Birkenhead's history can be traced back to an ancient building, the Priory, which was founded between 1154 and 1199 and stood on a lonely headland of birch trees. The Priory has now officially been declared an Ancient Monument. After King John granted Liverpool its charter, in the early 13th Century, the monks introduced the first ferry service across the river in 1330 from the Priory. When trips were not possible due to bad weather, passengers were accommodated in the Priory. The service was originally free, but increased demand meant that the monks could no longer afford to do this and they had to start charging a fee.