Redomiciled from Delaware, United States, on October 25, 1999, the company conducts most of its business through its insurance subsidiaries and other affiliates.

[1] The company owned the automobile insurer Esurance before selling it to Allstate for $1 billion.

[3] When Byrne took Fireman's Fund public in 1985, it was the largest IPO in American history,[4] and the insurer was sold to Allianz six years later.

[5] Upon completion of the Fireman's Fund sale in 1991, the remaining holding company and residual assets formed the starting point for the future White Mountains.

[1] White Mountain Insurance's current director is CEO George Manning Rountree.