Arthur J. Gallagher & Co.
One of the world's largest insurance brokers, this company helps businesses and individuals buy insurance and manage risk, placing policies, providing claims administration, and offering benefits consulting under names like Gallagher Re. It was founded in Chicago in 1927 by Arthur J. Gallagher, who put his own name on the door and took personal responsibility for every policy sold. In 1938 it wrote Chicago's first large-deductible fire insurance policy, for a dairy company, pioneering the modern risk-management field.
Estimated from filings — the split-adjusted price range over the quarters each manager built the position. A range, not a fill price; 13F reports a quarter-end snapshot, not a trade date.