I am looking for my niece adopted out by my minor aged sister in 1965 around Washington dc, last name HIRSCH, mothers name Linda Ruth, grandparents, Harriett and WIlliam Hirsch, birthed at girls home? No idea exact info.

Synnen has covered this several times - her post is very comprehensive.

https://www.askmehelpdesk.com/adoption/how-do-you-find-your-birth-parents-closed-adoption-398165.html

Because she is your biological niece, and not your biological child, you may be limited on what you can and cannot do to establish contact. For instance, the adoption agency probably will not give you ANY information, nor allow you to leave information with them.

Registering on reunion websites is probably your best free bet. If you're willing to put money into it, you could always hire a private detective.