Most Adoptions are Unofficial
Genealogists love records. But adoptions are one of those situations
that present problems. Throughout much of American history adoptions
were "informal" with couples simply taking the child in with no
"paperwork." And when there was legal paperwork, those records are often
closed.
But don't be surprised if there's no "documentation" to provide evidence
of an adoption. Many before the World War I era fall into the category
of "unofficial."