That makes it the third U.S. company to top $1 trillion in market capitalization.
Microsoft Corp. co-founder Gates has once again accrued a fortune worth exactly $100 billion.
The letter was addressed to Microsoft CEO Satya Nadella and President Brad Smith.
Microsoft maintained its lead, but Apple is staging a comeback.
The new 7-year deal aims to lower overall health-related costs.
Amazon shares closed up more than 3 percent, pushing the e-commerce giant’s market capitalization to $796.8 billion.
The country has always depended on access to the best technology American companies make, Microsoft President Brad Smith said.
Apple’s market capitalization is now about $847 billion, compared to Microsoft's $851 billion.