The couple plan to make the nine-bedroom home in the hills near Santa Barbara their permanent home, five months after formally stepping down as senior royals.
The 14,500 sq ft residence set in acres of land is on a private road giving the duke and duchess and their son Archie the chance for the privacy they have craved since the bombshell split from the royal family.
Ms Ragland, who is based 90 miles south in Los Angeles, has been helping to care for Archie and is reportedly seen by Meghan as her “rock”.
She was the only relative of the duchess to attend the couple’s wedding in May 2018.
Near-neighbours in the “California Riviera” include Oprah Winfrey and Ellen DeGeneres.
Features in the main house are said to include a library, office, spa with a separate dry and wet sauna, gym, games room, wine cellar and five-car garage. There is also a swimming pool and a tennis court.
The couple paid for the property from their own resources in July, the Evening Standard understands.
They still have access to Frogmore Cottage near Windsor Castle to use as their UK base. They have agreed to pay the taxpayer £18,000 a month to cover the £2.4 million cost of renovation of the property.
A source told the Page Six website: “They bought this house without help from his family, and they aren’t using it on loan from a friend as they had before. It’s truly theirs and they can’t wait to make it a home.”