Founded in New York City as Olcott & McKesson by Charles Olcott and John McKesson in 1833, the business began as an importer and wholesaler of botanical drugs. A third partner, Daniel Robbins joined the enterprise as it grew, and it was renamed McKesson & Robbins on Olcott's death in 1853.

From the middle of the 20th century, McKesson has derived a continually growing proportion of its income from medical technology rather than pharmaceuticals.

The company is one of the oldest continually operating businesses in the United States, and today, the corporation is among the largest in the USA, ranked 15th on the Fortune 500 list in 2005. It has an annual turnover of over $60 billion.

As well as offices throughout North America, McKesson also has bases in Europe (France, Netherlands and the UK) and Australia.

McKesson in the United Kingdom

In the United Kingdom, McKesson (operating as McKesson Information Solutions UK Ltd) acts solely as a provider of information technology services to the healthcare industry. In addition to numerous clinical software systems and finance and procurement services, McKesson also runs and maintains the Electronic Staff Record for the NHS, which upon completion of its rollout in 2007 will provide an integrated pay and HR system for 1.2 million staff - this will make it the world’s largest single HR/payroll IT system. Its UK base is in Warwick with data centres in Newcastle upon Tyne and Romford plus offices in Sheffield and Vauxhall, South London. Across the UK, it employs over 400 staff.