LEAVITT & CO.
367 Washington Street Boston
After July 1855, John B. Nichols was in partnership with Rufus Leavitt and the company name changed to Nichols, Leavitt & Co..
After July 1856 it was changed again to Leavitt & Co..
After July 1865 it was changed again to Leavitt Sewing Machine Co. .
By the 1870s, it was defunct.
The Nichols-Leavitt machines can be dated by their serial numbers approximately as follows:
| Serial Number | Year | Company |
| 1-28 up to July | 1853 | Nichols & Bliss |
| 29-245 " | 1854 | Nichols & Bliss -- J. B. Nichols |
| 246-397 " | 1855 | J. B. Nichols & Co. --- Nichols, Leavitt & Co. |
| 398-632 " | 1856 | Nichols, Leavitt & Co. --- Leavitt & Co. ? |
| 633-827 " | 1857 | Leavitt & Co. |
| 828-902 | 1858 | ” |
| 903-1115 | 1859 | ” |
| 1116-1436 | 1860 | ” |
| 1437-1757 | 1861 | ” |
| 1758-2077 | 1862 | ” |
| 2078-2400 | 1863 | ” |
| 2401-2900 | 1864 | ” |
| 2901-3900 | 1865 | " |
| 3901-4900 " | 1866 | Leavitt Sewing Machine Co. |
| 4901-5951 | 1867 | ” |
| 5952-6951 | 1868 | ” |
| 6952-7722 | 1869 | ” |
