In 1881, when Isabel was only five years old, she inherited approximately $3 million from her grandfather William Fletcher Weld, though this amount later increased to about $5 million after the Weld estate was probated. For more than a century, it was assumed that she had inherited $17 million from her grandfather, though that amount has been proven incorrect. The first erroneous report of the $17 million figure appeared when the "Boston Globe" ran a front page story on the Isabel's marriage to Larz Anderson in 1897. The historical record, however, shows the $17 million to have actually been the final value of William Fletcher Weld's $20 million estate, after other bequests and estate taxes were deducted, leaving a residual $17 million that was shared equally among Isabel and Grandfather Weld's three other grandchildren, William Fletcher Weld II, Charles Goddard Weld and Mary Bryant Weld.