A retired federal government attorney,who died June 24, left Arlington County Library nearly $800,000, which county officials believe to be the largest single gift it’s ever received.

Rosemarie G. Bowie, 76, who retired from the U.S. Patent and Trademark Office, was a frequent user of the county’s Central Library. In her will, she instructed that the proceeds from the sale of her north Arlington home and half her remaining estate be given to the library system, county officials said.

“The county clerk searched our archives back to 1936 and found nothing bigger” than this gift, said deputy county manager Mark Schwartz.

According to her death notice, Bowie was a long-time pro-bono guardian of Arlington residents in need. She also enjoyed travel, photography, sewing and ceramics.

A cousin who lives in Tucson said Bowie tried to quietly support others and the library with her gift.

“I was just blown away by such generosity,” said Diane Kresh, the library director. “My staff is humbled that we had such an impact on her that she’d leave her estate to us. It’s a really special gift.”

The donation specified that the proceeds of the sale of her home on Danville Street, and half of her remaining estate, should go to the library. Her home had an assessed value of $626,500 in 2013, and her executor told county officials that half of her remaining estate is worth well over $100,000.

Schwartz said it’s unlikely that the county will use the money to offset library operations, since most of its expenses are for salaries and other continuing expenses. It’s more likely that the money will be used for a one-time capital improvement or purchase. The County Board is expected to formally accept the gift at its Sept. 21 board meeting.