Authorities say the little girl fell at around 9 a.m. EDT Monday from an apartment on Bel Pre Road in Aspen Hill.
Capt. Paul Starks says either the girl or her 5-year-old brother may have opened the window and were looking outside prior to the fall.
Officials say the toddler was initially taken to Holy Cross Hospital and was then taken to Children’s Hospital.
The girl is said to be in serious but stable condition.
Detectives from the Family Crimes Division are now investigating the incident.