Forbes' 2026 list of America's 400 richest people requires a net worth of at least $4.4 billion, up $600 million from last year, driven by AI and stock market gains. Massachusetts billionaires leading the list include Abigail Johnson of Fidelity Investments ($41.6 billion), her brother Edward Johnson IV ($16.3 billion), Robert Kraft ($15.2 billion), and Elizabeth Johnson ($14.4 billion).