In 2018, 67 is the most common age for an American (U.S.) Harriet who is registered female with the Social Security Administration. It is the 867th most common female first name for living U.S. citizens.
― Anonymous User 10/5/2018
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The name Harriet was given to 179 girls born in the US in 2015.
Despite its popularity in the UK, the name Harriet is very uncommon nowadays for American babies. In 2012, it was only given to 89 little girls here. My guess would be that it has to do with the popularity of Harry in the UK, similar to how Georgina is popular in the UK and so is George, but both are relatively uncommon in the US.