MacArthur Foundation — Founder (text): John D. MacArthur

NoteThe source directly confirms that John D. MacArthur is one of the founders of the MacArthur Foundation. The Wikidata page explicitly lists 'John D. MacArthur' under the 'founded by' property. The claim asks for the founder as text value, and the source provides exactly this: 'John D. MacArthur' as a text entry (not an entity reference). Note that Catherine T. MacArthur is also listed as a co-founder, making this a partial listing of founders, but the claim's specific assertion about John D. MacArthur being a founder is accurate and confirmed.