How long does it take to adopt?
To adopt an infant domestically in the United States it takes about 12 months with most placements happening between six and 18 months. This is the time between "going on the books" when your homestudy is completed to the time when a placement is made.
The wait time can be affected by many factors, one of the largest being how open the adoptive family's profile is. For example, a family only prepared to adopt a child of one ethnic background could potentially wait much longer than a family open to a child of any background.
And finally, these are all averages, and there is no way to predict how long it will take for any particular family to find the birthparents they were meant to match with.