The ranks of the peerage are duke, marquess, earl, viscount, and baron.
The last non-royal dukedom was created in 1900, and the last marquessate in 1936. Creation of the remaining ranks mostly ceased once Harold Wilson's Labour government took office in 1964, and only four non-royal hereditary peerages have been created since then. These were:
Until the House of Lords Act 1999 was passed, all peers of the United Kingdom were automatically members of the House of Lords. However, from that date, most of the hereditary peers ceased to be members as part of Parliamentary reform, whereas the life peers retained their seats. All hereditary peers of the first creation (i.e., those for whom a peerage was originally created, as opposed to those who inherited a peerage from an ancestor), and all surviving hereditary peers who had served as Leader of the House of Lords were offered a life peerage in order to allow them to sit in the House should they wish.