Former Owner
- John McRay1
- John Roland Abbey1
- John Rolls, 1st Baron Llangattock1
- John Ruskin1
- John Sidney Hawkins1
- John Singer Sargent1
- John Stirton1
- John Stow1
- José Fernando Ramírez1
- Julius Heinrich Jeidels1
- Justin MacCarthy Reagh1
- Kartause Erfurt1
- Klaus Dieter Dahmen1
- Lambach Abbey1
- Laurence Kirby1
- Laurence Vaux1
- Leonello d'Este, Marquis of Ferrara1
- Llewelyn Lloyd-Mostyn, 3rd Baron Mostyn of Mostyn1
- Long Island Historical Society, Maine1
- Louis Charles Karpinski1