Nancy Johnson patented the hand-cranked ice-cream freezer in 1843.
Her design used a container surrounded by an ice-and-salt freezing mixture, with a dasher turned by a crank. The movement helped freeze the mixture evenly while reducing the formation of large ice crystals.
Johnson’s freezer was an important improvement because it made homemade ice cream easier and more consistent than earlier methods. The patent was granted to her on September 9, 1843, although she did not manufacture the device commercially herself.
The invention is sometimes wrongly attributed to William Young, whose 1848 patent improved the design by enclosing the mechanical parts. Johnson’s freezer remains a key step in the history of household ice-cream making.