| Surname | Country | State | County or Province | From | To | Member |
|---|---|---|---|---|---|---|
| Taber | A010-1 | |||||
| Taft | USA | Ohio | Fulton County | 1790 | 1900 | B035-1 |
| Taft | USA | Michigan | Kalamazoo County | 1790 | 1900 | B035-1 |
| Taft | USA | Ohio | Lucas County | 1800 | 1900 | B035-1 |
| Taft | USA | Ohio | Wood County | 1800 | 1900 | B035-1 |
| Taft | USA | Michigan | Lenawee County | 1800 | 1900 | B035-1 |
| Tague | USA | Pennsylvania | F008-1 | |||
| Tambourine | USA | Illinois | 1921 | 1952 | J009-1 | |
| Tanner | Switzerland | Appenzell | Teufen | 1615 | 1690 | B018-1 |
| Tanner | Switzerland | Appenzell | Speicher | 1615 | 1690 | B018-1 |
| Tardeil/Tardeigll | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1680 | 1874 | J009-1 |
| Tatara | Austria-Hungry | Brezova | 1850 | Present | H014-1 | |
| Taylor | Canada | Newfoundland | bef 1910 | D005-1 | ||
| Tegeler | USA | Missouri | Gasconade County | 1850 | J005-1 | |
| Tegeler | Germany | Minden | J005-2 | |||
| Telfhorster | Prussia | E005-1 | ||||
| Telfhorster | Westfalia | E005-1 | ||||
| Terrell | USA | PA | Fayette | 1810 | 1920 | B020-1 |
| Thomas | USA | Illinois | Cook County (Chicago) | 1863 | present | B026-2 |
| Thomas | USA | Virginia | 1750s | M011-1 | ||
| Thomas | USA | North Carolina | 1750s | M011-1 | ||
| Thomas | USA | Illinois | St. Clair County | 1818 | present | M011-1 |
| Thommes | Germany | Trier | 1700 | Present | T011-1 | |
| Thompsen | Denmark | Droninglund | Asa | J009-1 | ||
| Thompson | Ireland | County Limerick | 1830 | 1860 | B026-2 | |
| Thompson | USA | Illinois | Cook County (Chicago) | 1860 | present | B026-2 |
| Tibbetts | England | Norfolk County | 1800 | present | A010-1 | |
| Tibbetts | USA | Iowa | 1800 | present | A010-1 | |
| Tibbetts | USA | Wisconsin | Dane County | 1800 | present | A010-1 |
| Tibbs | USA | Kentucky | Graves County | 1800 | present | M012-1 |
| Tielman | Germany | Westphalia | Mehner, Masch | 1700 | 1820 | B018-1 |
| Tiltges | Luxembourg | Niederfeulen | 1700 | present | S005-1 | |
| Tilton | USA | Vermont | Rutland County | 1830 | 1850 | P003-2 |
| Tilton | USA | Ohio | 1840 | 1900 | P003-2 | |
| Tomaso | Italy | Basilicata | Potenza | 1864 | 1921 | J009-1 |
| Tomaso | USA | Illinois | 1921 | 2007 | J009-1 | |
| Tomaszewski | USA | Illinois | 1900 | 1970 | D016-1 | |
| Tomaszewski | Poland | 1900 | 1970 | D016-1 | ||
| Tomson | A010-1 | |||||
| Tordo/Tordol | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1540 | 1726 | J009-1 |
| Toretta | France | Provence-Alpes-Côte-d'Azur | Alpes-Maritimes | 1660 | 1730 | J009-1 |
| Torpey | Ireland | Leitrim | 1800 | Present | T011-2 | |
| Tottle | England | Devon | 1830 | 1899 | D011-1 | |
| Townsend | USA | Maryland | A007-1 | |||
| Townsend | USA | Ohio | Meigs County | A007-1 | ||
| Trandel | Poland | Gdansk | 1830 | 1870 | T004-1 | |
| Trandel | Poland | Pommerania, Glowin | 1832 | ? | T004-1 | |
| Traunner | USA | West Virginia | A007-1 | |||
| Traunner | USA | Ohio | A007-1 | |||
| Traut | Germany | Neidersachen | 1700 | 1832 | P003-1 | |
| Traut | USA | Ohio | Summit County | 1832 | 1846 | P003-1 |
| Traut | USA | Wisconsin | Milwaukee County | 1846 | 1865 | P003-1 |
| Traut | USA | Minnesota | Dakota County | 1865 | 1900 | P003-1 |
| Trayers | Ireland | 1850 | M001-1 | |||
| Trayers | USA | Michigan | Wayne County | 1850 | 1905 | M001-1 |
| Trayers | USA | California | 1850 | 1905 | M001-1 | |
| Treichel | Germany | Pommern | S035-1 | |||
| Treichel | USA | Illinois | Cook County | 1840 | 1956 | S035-1 |
| Trevathan | USA | North Carolina | J009-1 | |||
| Trevathan | USA | South Carolina | J009-1 | |||
| Trippler | USA | Wisconsin | Manitowoc County | B016-1 | ||
| Trogolo | Italy | Lusiglie (Torino) | W006-1 | |||
| Trogolo | USA | Illinois | Bureau/Piedmont Counties | 1901 | present | W006-1 |
| Trout | Germany | Neidersachen | 1700 | 1832 | P003-1 | |
| Trout | USA | Ohio | Summit County | 1832 | 1846 | P003-1 |
| Trout | USA | Wisconsin | Milwaukee County | 1846 | 1865 | P003-1 |
| Trout | USA | Minnesota | Dakota County | 1865 | 1900 | P003-1 |
| Trovillo | USA | Pennsylvania | 1720 | 1880 | B023-1 | |
| Trovillo | USA | Ohio | 1720 | 1880 | B023-1 | |
| Trukoszy | Hungry | City Budapest | 1800 | 1900 | H011-1 | |
| Truman | USA | PA | Fayette/Washington | 1773 | 1920 | B020-1 |
| Trygstad | Norway | Telemark | Verdalen | 1846 | 1931 | O001-1 |
| Trygstad | USA | Minnesota | Hennepin County | 1846 | 1931 | O001-1 |
| Trygstad | USA | Minnesota | Goodhue County | 1846 | 1931 | O001-1 |
| Trznadel | Poland | Gdansk | 1830 | 1870 | T004-1 | |
| Tunze | Germany | Saxony | G015-1 | |||
| Tuohy | USA | 1700 | present | C001-1 | ||
| Tuohy | Ireland | 1700 | present | C001-1 | ||
| Turner | USA | Virginia | 1765 | 1805 | S029-1 | |
| Tuttle | A010-1 | |||||
| Tuttle | M026-1 | |||||
| Tyley | United Kingdom | M028-1 | ||||
| Tyley | USA | Illinois |