| Surname | Country | State | County or Province | From | To | Member |
|---|---|---|---|---|---|---|
| Abbott | Ireland | 1800 | Present | T011-2 | ||
| Abrahamson | Norway | G013-1 | ||||
| Adamson | USA | Texas | P013-1 | |||
| Albonetti | Italy | Emilia Romagna | Ravenna | 1790 | 1908 | J009-1 |
| Aldoprando | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1874 | 2000 | J009-1 |
| Alexander | Germany | Baden | Oldenburg | 1848 | present | H018-1 |
| Alger | USA | Indiana | Wabash County | 1890 | B031-1 | |
| Algire | USA | Pennsylvania | Berks County | 1700 | 1830 | G001-1 |
| Allaisa/Allaiso/Alasi | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1550 | 1750 | J009-1 |
| Allavena | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1570 | 1670 | J009-1 |
| Allen | USA | New York | New York City | 1780 | 1840 | S009-1 |
| Allind | USA | Illinois | Cook County | 1870 | present | W006-1 |
| Altherr | Switzerland | Appenzell | Speicher | 1560 | 1700 | B018-1 |
| Altimes | Ireland | Limerick | 1790s | A001-1 | ||
| Alton | Ireland | Limerick | 1790 | A001-1 | ||
| Alton | USA | New York | Jefferson County | 1830s | A001-1 | |
| Alton | USA | Minnesota | Wadena County | 1830s | A001-1 | |
| Alton | USA | Wisconsin | 1830s | A001-1 | ||
| Amick | USA | Indiana | Scott County | C006-1 | ||
| Andersen | Denmark | Moen | Frenderup | 1850 | J009-1 | |
| Anderson | USA | Illinois | 1892 | present | A005-1 | |
| Anderson | Sweden | bef 1892 | A005-1 | |||
| Anderson | A008-1 | |||||
| Anderson | Sweden | Frändefors | Älusborg | Early 1700's | B019-1 | |
| Anderson | G013-1 | |||||
| Anderson | Sweden | Alusborg | 1800 | 1890 | J003-1 | |
| Anderson | Sweden | bef 1883 | B019-1 | |||
| Anderson | USA | Illinois | Cook County | 1890 | present | J003-1 |
| Anderson | USA | Illinois | Cook County | 1882 | 1948 | B019-1 |
| Andorfer (Arndorfer) | Germany | 1800 | present | A010-1 | ||
| Andorfer (Arndorfer) | USA | Wisconsin | Walworth County | 1800 | present | A010-1 |
| Andorfer (Arndorfer) | USA | Wisconsin | Dodge County | 1800 | present | A010-1 |
| Andreis/Andrea/André dit Bandetto | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1511 | 1820 | J009-1 |
| Andrews | M026-1 | |||||
| Andruss | A010-1 | |||||
| Angermeier | USA | Illinois | Cook County | 1910 | 1950 | B023-1 |
| Ansaldo/Ansauda | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1570 | 1642 | J009-1 |
| Ardoin/Ardoina/Ardoino | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1490 | 1780 | J009-1 |
| Armstrong | USA | Michigan | M026-1 | |||
| Aschier/Aschiero | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1478 | 1625 | J009-1 |
| Aspel | USA | Illinois | Cook County | 1860s | present | N001-2 |
| Aspel | USA | Illinois | DuPage County | 1860s | present | N001-2 |
| Aspel | USA | Illinois | Kane County | 1860s | present | N001-2 |
| Aspel | USA | Illinois | Will County | 1860s | present | N001-2 |
| Aspil | Ireland | Dublin County | 1800 | 1900 | N001-2 | |
| Aspill | Ireland | Dublin County | 1800 | 1900 | N001-2 | |
| Ater | Germany | M025-1 | ||||
| Ater | USA | Illinois | Piatt County | M025-1 | ||
| Atkinson | USA | Ohio | Morgan County | 1828 | A007-1 | |
| Atkinson | USA | Ohio | Perry County | 1828 | A007-1 | |
| Atkinson | USA | Iowa | 1828 | A007-1 | ||
| Atkinson | USA | Kansas | 1828 | A007-1 | ||
| Atkinson | USA | Oklahoma | 1828 | A007-1 | ||
| Auchincloss | Scotland | Paisley | A002-1 | |||
| Auda | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1600 | 1713 | J009-1 |
| Augiera | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1590 | 1731 | J009-1 |
| Aureglia/Aureglio/Aurelio/Aurelli | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1570 | 1810 | J009-1 |
| Austin | USA | Wisconsin | Sauk County | 1870 | 1910 | A009-1 |
| Ayers | USA | Pennsylvania | 1805 | A007-1 | ||
| Ayers | USA | Ohio | 1805 | A007-1 | ||
| Ayers | USA | Michigan | 1805 | A007-1 |