The global accounting giant built on a 1924 Chicago startup

Countries & Cities · Published 15 October 2026 Swipe more like this →

In short: Grant Thornton is a powerhouse of global finance, but its roots are surprisingly local. From a single senior accountant's vision in Chicago to a multinational network of 73,000 people, the firm's journey reflects the evolution of modern professional services and the complexities of global auditing.

The firm's lineage is a tapestry of mergers spanning over 180 years. The 'Grant' name traces back to 1924, when Alexander Grant & Co was founded in Chicago by a former senior accountant at Ernst & Ernst. Grant's specific mission was to provide dedicated services to mid-sized companies. Meanwhile, the 'Thornton' side of the name originated in Oxford in 1904 with Thornton and Thornton, eventually merging with Baker & Co in 1959 to become Thornton Baker. These two distinct lineages finally converged in 1980 when they joined with 49 other firms to form the global organization known as Grant Thornton.

Today, the network operates as a non-profit, non-practicing international umbrella entity. It consists of independent member firms across 147 markets. This structure means that while they share a brand and global reach, each member firm is a separate national entity that manages its own administrative matters and local governance. The network provides assurance, tax, and advisory services, generating a combined global revenue of approximately US$7.5 billion.

The firm's history is also marked by significant regulatory scrutiny and high-stakes transactions. In recent years, the UK arm has faced various fines for audit misconduct and 'scepticism failure' regarding companies like Patisserie Valerie and Interserve. Following unsuccessful merger bids with international entities, Grant Thornton UK reached a deal with Cinven in November 2024 to divest its majority interest for roughly £1.3 billion.

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