- Long (continued)
- Longdon
- Longenecker
- Longespee
- Longhurst
- Longwell
- Lonsbury
- Loo
- Looby
- Looker
- Loomis
- Loop
- Loper
- Jacob (Est 1622-Est 1651)
- Lopez
- Lord
- Lorenz
- Lorette
- Lorhetta
- Lorince
- Loring
- Lorow
- Lorraine
- Losee
- Losey
- Losito
- Lostroh
- Lothrop
- Lott
- Lou
- Loud
- Loutzenhiser
- Love
- Loveland
- Loveless
- Lovell
- Loveridge
- Lovering
- Lovett
- Loveys
- Lovin
- Low
- Lowe
- Lowers
- Lowman
- Lown
- Lowther
- Loy
- Lozon
- Lucas