Babies
In the early 19th century, parents believed babies would literally grow crooked if they were allowed to move freely. Their clothing, therefore, "allowed no more movement than a turn of the head---sometimes not even that," according to costume historian Clare Rose in her book "Children's Clothes." Babies were swaddled tightly in cloth, with the arms held straight against the baby's sides. To further confine movement, a "stayband" of fabric was placed under one or two head caps and pinned to the baby at the shoulders or torso. Babies of both genders wore gowns so long that crawling was difficult if not impossible.
Girls
In the early 1800s, girls wore dresses with raised waistlines, relatively narrow skirts and short sleeves. As throughout the remainder of the 19th century, girls' dresses mirrored women's closely. As the Victorian period began, waistlines dropped to their natural position and skirts became fuller. Eventually, many layers of petticoats were replaced with crinolines --- wire cages worn to make skirts stand well away from the body. Throughout the early 19th century, necklines were often quite low, even for very young girls.
Boys
Boys wore dresses until they were 4 to 6 years old, after which they wore long pants. "There was no transitional costume...between frocks and suits, which were a near approach to the attire of manhood," wrote fashion historian Moore in "The Child in Fashion." "The change was made abruptly." With the wearing of long pants came white shirts, vests and jackets. Ties were sometimes worn, as well, but often in the form of bows.
Accessories
Baby accessories consisted mostly of cloth caps, bibs and booties. Girls wore hats as elaborate as their mother's, as well as gloves, stockings and shoes --- even high-heeled ones. Girls might also carry parasols and purses, and they always wore corsets. Boys wore hats often similar to their father's.