Kathleen Magowan may have passed away in 2011 at the age of 87, but her surprising charitable donations have given her a very unexpected legacy: she's being called a "secret millionaire."

During her lifetime, the former first grade teacher and her twin brother, Robert, amassed a fortune of nearly $10 million, much to the surprise of residents in their community of Simsbury, Connecticut.

Kathleen Magowan's estate alone was estimated at nearly $6 million and after her passing she willed sizable sums of her wealth to places she held dear.

She left nearly $480,000 to Simsbury public schools, $500,000 to the University of St. Joseph in West Hartford, more than $400,000 to the McLean nursing home where she died, and nearly $375,000 to her local parish, St. Mary's Roman Catholic Church, according to The Hartford Courant.

"Her donation was the biggest in at least 33 years," Katie Wilde, executive assistant to the superintendent of Simsbury Public Schools, told Yahoo News.

Magowan taught for 35 years in the district and loved chatting about books and teaching, according to people who knew her, even in her later years at McLean Continuing Care Community, where she was a resident until her passing.

"She was very much the schoolteacher. She became a part of the community when she joined our pool. She was always recommending books and having discussions in the pool," Deene Morris, Director of Development at McLean tells Yahoo.

"People remember that she faithfully attended all exercise classes and had an attendance record that nearly exceeded all residents. She lived her life fully and completely, until the end of her life," Morris added.

However, none of the residents at McLean were aware of Magowan's affluence.

Neither Magowan nor her brother ever married and their fortunes were never mentioned in their obituaries. Robert Magowan, who worked for Prudential Insurance, died one year prior to his sister.

It reportedly took lawyers two years to discover the entirety of their massive wealth, which was amassed through a series of smart investments, according to The Hartford Courant:

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"In one of the most stunning discoveries, a neighbor who was helping the attorneys found a Quaker Oats can in a closet that contained the original war bonds from the 1940s and 1950s, largely in small denominations of $50 and $100. The attorneys had no idea what the bonds might be worth, but some research on the Internet showed that the papers in the Quaker Oats can were worth $183,000."

"They didn't throw anything away," attorney David Bondanza, who did much of the legal work on the estate, told The Courant. "That's the bottom line. There was a lot of history in that house.''

The contents of their home reportedly added $10,000 to their estate after lawyers found $6,000 in jewelry in a safe deposit box. The Magowan twins' list of priceless items go on, with National Geographic magazines dating back to 1929, old newspapers, dozens of file folders filled with magazines, record albums from the 1920s along with a record player that still worked.

However, the most important lesson from their savings seems to be in the power of giving.

"People don't give to be recognized," Morris tells Yahoo. "Miss Magowan has shown great generosity."