Alnwick Castle was the home of the most powerful medieval northern baronial family, the Earls of Northumberland.

It was held by the De Vesci family (now spelt "Vasey" – a name found all over south-east Northumberland) for over 200 years, and then passed into the hands of the House of Percy in 1309.

[6] At various points in the town are memorials of the constant wars with the Scots, in which so many Percys spent the greater part of their lives.

A cross near Broomhouse Hill across the river from the castle marks the spot where Malcolm III of Scotland was killed, during the first Battle of Alnwick in 1093.

At the side of the broad shady road called Ratten Row, leading from the West Lodge to Bailiffgate, a stone tablet marks the spot where William the Lion of Scotland was captured during the second Battle of Alnwick in 1174 by a party of about 400 mounted knights, led by Ranulf de Glanvill.

[13] According to historian Dan Spencer, this made Alnwick the most besieged place in the country in the Wars of the Roses.

[14] Sir Thomas Malory mentions Alnwick as a possible location for Lancelot's castle Joyous Garde.

[19] A Royal Air Force distribution depot was constructed at Alnwick during the Second World War with four main fuel storage tanks (total capacity 1700 tons) and road and rail loading facilities.

[30] The castle has extensive grounds landscaped by Capability Brown, which include several follies as well as the ruins of St Leonard's Hospital, Alnwick Abbey and Hulne Priory.

The town centre is the marketplace, with its market cross, and the 19th century Northumberland Hall, used as a meeting place.

[34] Other places of interest in and near the town include: Local news and television programmes is provided by BBC North East and Cumbria and ITV Tyne Tees.

[51] The East Coast Main Line between Edinburgh (journey time approximately 1:10) and London (journey time approximately 3:45) runs through Alnmouth for Alnwick Station – about 4 miles (6 km) away – with a weekday service of 15 trains per day north to Edinburgh and 13 trains per day south to London.

Since the 2010s, the Aln Valley Railway Trust have worked to reopen the branch as a heritage railway but, due to construction of the A1 Alnwick bypass removing a section of the original trackbed on the edge of the town, their purpose-built Alnwick Lionheart terminus is located near the Lionheart Enterprise Estate on the outskirts of the town.

The reopening project is ongoing and, as of July 2020, the line's eastern terminus had reached a new station at Greenrigg Halt, approximately 1.5 miles (2.4 km) from Lionheart, although it is yet to carry passengers over the full length.