1850 - present: Modern wire-nails (nails that are round in cross-section) appeared in North America in the 1850s and continue to the present. Round or wire nails are produced by cutting a round drawn wire into lengths to which a point and head are added by the machine.

When did they stop using iron nails?

From the late 1880s through the 1890s steel gradually replaced wrought iron in the manufacture of cut nails (Heitmann 1989:30). From 1884 through 1886 only 5% of cut nails were made of steel. By 1891 three quarters of all cut nails were made of steel. Before the end of the century all cut nails were made of steel.