Infant boys and girls were dressed the same until they were "well toilet trained". It is difficult to distinguish a little boy from a little girl in older photos of the 1800s. One can get a hint by looking at how the hair was styled. Typically a boys hair was parted on the side while a girl's hair was parted down the middle. An infant through the age of toddler wore a dress or gown. As soon as they were toilet trained with minimal "accidents" boys were dressed in a shirt and pants and girls in dresses.
Dresses, aprons, pinefores, petticoasts, and pantaloons
TODDLER /BOY'S CLOTHING & ACCESSORIES
A toddler's clothes were a bit different from an older boy's in design. The shirt was buttoned to the pants for toddlers. His ensemble may opr may not have had a jacket. Note the hemline of the pants. Pants or nickers could be open at lower leg or gathered and cuffed. The pants could be hemmed anywhere from the knee down. As a youngster grew his clothing style changed with him until his cothing mimiced that of adult men.