| Surname | Data | Member # |
| LAFLIN | Saugerties, Ulster Co., NY; Frontier, Clinton Co., NY | K143 |
| LAIGHT / LYGHT / LAIGHTY | New Winsor, NY; Andes, Delaware Co., NY; Monroe Co., NY; Winsor, Ontario | B175 |
| LAKE | Scipio, Sempronius & Niles, Cayuga Co,. NY; CT; NY; OH; MI; IN | M513 |
| LALONDE / LALONE | Carthage, NY | P221 |
| LAMB | Ballston Spa, NY | S578 |
| LAMON | Houndsfield, Jefferson Co., NY | B511 |
| LAMPMAN | Rome & Swanton, NY | E089 |
| LANDON | Columbia Co., NY; Johnstown, NY | G229 |
| LANDON | Wayne, Monroe & Ontario Co., NY | M165 |
| LANE | NY | R139 |
| LANE | Fayette, ME; Kingfield, ME | R139 |
| LANE | CT; Oswego Co., NY | R213 |
| LANE/MCLANE | Cayuga Co., NY; Van Buren Co., MI | J121 |
| LANG | Belfast, Allegany Co., NY; Michias, NY; Wyoming Co., NY | B545 |
| LANGWORTHY | Adam Center, NY | D291 |
| LANSING | Albany Co., NY | W416 |
| LAPLANTE | Erie Co., NY; Canada | M505 |
| LAPREE | Franklin Co., NY | H286 |
| LARKIN | Chenango Co., NY | A166 |
| LAW | Broome Co., NY | V059 |
| LAW | Canada; Russell & Pierrepont, St. Lawrence Co., NY | L181 |
| LAWLESS | Co. Wexford, Ireland; Syracuse, NY; Kingston, Ontario, Canada | S550 |
| LAWLOR | NJ; NY; Ireland | M416 |
| LAWRENCE | Cape Vincent, Jefferson Co., NY | C426 |
| LAWRENCE | New York City, NY; Wayne Co., NY | R275 |
| LAYMAN | Jefferson Co., NY | W373 |
| LEAR | Franklin & Bedford Co., PA; Brown Co., IL | T133 |
| LEARNED | MA; VT; NY | M456 |
| LEE | Smithville, NY; CT | H373 |
| LEE | Saratoga Co., NY | H412 |
| LEE | Skaneateles & Marcellus, NY | W224 |
| LEET | Stony Point, Rockland Co., NY | E097 |
| LEET | CT; Stony Point, Rockland Co., NY | N097 |
| LEIBFRIED | Germany; New York City; Syracuse, NY | S541 |
| LENWAY | Carthage, NY | P221 |
| LESTER | Ledyard, Genoa, Scipio & Sempronius, Cayuga Co., NY; NY; OH; MI | M513 |
| LETTS | NJ; Tompkins Co., NY | K192 |
| LEWIS | Erie Co., NY | M499 |
| LEWIS | Broome Co., NY | S394 |
| LIGHT (+var) | NY; PA VA; CA; WA; NM | B175 |
| LIGHT / LEIGHT / LAIGHT (+var) | Rochester, Afton, Tioga, Mayfield and Rochester, NY | B175 |
| LILLIE | St. Lawrence Co., NY | B548 |
| LINCOLN | Wayne & Erie Co., NY; OH; Shepard Settlement, Onondaga Co., NY | M447 |
| LINTON | MD, Jefferson Co., NY | M488 |
| LITTLEFAIR | Otsego & Chenango Co., NY | V059 |
| LITZ | Saugerties, NY | S578 |
| LOBDEL | Cattaraugus Co., NY | C409 |
| LONG | St. Lawrence Co., NY | B548 |
| LORD | Genesee, Chenango & Greene Co., NY | E106 |
| LORY | CT; Hyndsville, Scloharie Co., NY; Tioga Co., NY | D256 |
| LORY | Apalachin, NY; Poughkeepsie, NY | D256 |
| LOSS | Madison, Onondaga, Monroe & Oneida Co., NY | L226 |
| LOUGHLEY | Canada; St. Lawrence & Oswego Co., NY | B517 |
| LOVERING | NY | R139 |
| LUCAS | Homer, NY | S519 |
| LUDDINGTON | NY; Jackson Co., MI | D219 |
| LUDDINGTON | Oswego & Herkimer Co., NY | H294 |
| LUMLEY | NY; WI; KS; TX | C339 |
| LURCOCK | NY (Southern Tier); PA (Northern) | D257 |
| LYNCH | Ireland; Madison Co., NY | B510 |
| LYNCH | Ireland; Syracuse and Onondaga Co., NY | P268 |
| MACDOUGALL | North Argyle, NY; Dutchess Co., NY | E089 |
| MACE | Wyoming Co., PA | B556 |
| MACMILLAN | Oswego Co., NY; Ontario, Canada; | C409 |
| MAGEE | Ireland; Warren Co., NY | M447 |
| MAHAN | Ireland; Syracuse, NY | P268 |
| MAILLOUX | NY; MA; VT | S597 |
| MALONEY | Ithaca, Tompkins Co., NY | W394 |
| MANAHAN | Split Rock, Marcellus & Syracuse, NY | R294 |
| MANAUGH/MANY | Quebec, Canada; Middlebury, VT | R139 |
| MANDEVILLE | Horseheads, NY; Broome Co., NY; Oxford, Chenango Co., NY | M447 |
| MANERY | VT; Washington Co., NY | R139 |
| MANN | Columbia & Brome Co., NY; Scottland | R275 |
| MANNING | NY; NJ; OH | H341 |
| MARCY | Utica & Albany, NY | B260 |
| MARE / MAARE | St. Lawrence & possibly Washington Co., NY | C368 |
| MARKHAM | MA; CT; NY; MI; WI; OR; WA | H388 |
| MARSDEN | Oneida & Oswego Co., NY | M505 |
| MARSH | Nova Scotia | B197 |
| MARSHALL | Oswego & St. Lawrence Co., NY | C459 |
| MARTIN | Dutchess & Chautauqua Co, NY | M475 |
| MARTIN | MA; Rensselaerville, NY; Oxford Co., Ontario, Canada | F171 |
| MARVIN | Oneida & Oswego Co., NY; CT | W209 |
| MASON | Schroon, Essex Co., NY | D146 |
| MASON | Monroe Co., NY | M165 |
| MASONHEIMER | Allegheny Co., PA | P270 |
| MATTISON/MATTESON | W. Greenwich, RI; Shaftsbury, VT; Town Albion, Oswego Co., NY | B462 |
| MATTOON | NY | A150 |
| MAYNARD | Steuben Co., NY; CT | L190 |
| MAYNE | St. Lawrence Co., NY | Y030 |
| MCALPINE |