Unless these older cookbooks have specific local focus of historic value and are first edition hardcover books, if you should donate to an existing local library, those books might be given away or sold in a fundraising campaign for the library to acquire new books.

Public libraries are under pressure in terms of space planning for the future and always, the budget to buy new books.

Is there a culinary school in your region that you could email to the school director to gauge the level of interest for your collection by the students themselves? If you are serious about this, it might be more efficient to provide a list of the book titles or at least the type of cuisine these books may cover. if you blog, post that list or photo of choice texts online.

I suspect the nature of the recipes may have changed to reflect changed regional dietary preferences of today. Those cookbooks could be great examples....not all, but some titles.

Or to go to a foodblogger's website living in your area and make arrangements to send electronic info about your collection.

Just some ideas. Promote it to the audience who would best value the cookbooks/recipes for many different reasons.

OR if there is new restaurant opening up, would they want a few as part of their "decor"?

From a librarian.