Prior to the 19th century, children were dressed as miniature adults…

18th c. Girl With a Kitten, Jean-Baptiste Perronneau
Children’s fashion often preceded similar changes in adult clothing. Simple frocks for girls in the closing decades of the 18th century foreshadowed the fashionable high-waisted, neo-classical style that would become popular for women during the first decades of the 19th century.

1790 Portrait of a Girl, John Hoppner
This pastoral image of a young girl by Thomas Gainsborough is a reminder that poor girls wore “tattered hand me downs or clothes made of coarse woollens and rougher cottons or mixtures like fustian.” (Fashion-Era)

Cottage Girl with Dog and Pitcher, Gainsborough, 1785
The easy, loose-fitting shifts below made it easy for little girls to play. The little boy’s skeleton suit is described in the post below.

The Sackville Children, John Hoppner 1797
A little girl’s mourning dress in 1809, although black, remained comfortable and unrestrictive. More details about this dress are at this link from Jessamyn’s Regency page.

Mourning dress, Ackermann plate, 1809
Childrens’ fashion posts on this site: