MCFI is the usual name of Massachusetts Convention Fandom, Inc., a US 501(c)3 tax-exempt organization which is chartered to run conventions, primarily Worldcons. It ran Noreascon Two, Noreascon 3 and Noreascon 4. It was founded at a party in July, 1974 in Boxboro, MA.
(It did not run Noreascon I, which predated MCFI. Noreascon I was run by a special-purpose organization which dissolved a few years after the convention, turning its remaining assets over to NESFA in exchange for NESFA publishing the Noreascon Proceedings.)
In addition to Worldcons, MCFI has also run three Smofcons (Smofcon 3, Smofcon 15, and Smofcon 25), the 1999 World Fantasy Convention, and the 1998 Ditto. Non-convention-running activities included running the Connie Bailout, the masquerade at Iguanacon, and acting as US financial agent for Aussiecon 4.
See also the MCFI website.