The term “metropolitan city” means (A) a city within a metropolitan area which is the central city of such area, as defined and used by the Office of Management and Budget, or (B) any other city, within a metropolitan area, which has a population of fifty thousand or more. Any city that was classified as a metropolitan city for at least 2 years pursuant to the first sentence of this paragraph shall remain classified as a metropolitan city. Any unit of general local government that becomes eligible to be classified as a metropolitan city, and was not classified as a metropolitan city in the immediately preceding fiscal year, may, upon submission of written notification to the Secretary, defer its classification as a metropolitan city for all purposes under this chapter, if it elects to have its population included in an urban county under subsection (d). Notwithstanding the second sentence of this paragraph, a city may elect not to retain its classification as a metropolitan city. Any city classified as a metropolitan city pursuant to this paragraph, and that no longer qualifies as a metropolitan city in a fiscal year beginning after fiscal year 1989, shall retain its classification as a metropolitan city for such fiscal year and the succeeding fiscal year, except that in such succeeding fiscal year (A) the amount of the grant to such city shall be 50 percent of the amount calculated under section 5306(b) of this title ; and (B) the remaining 50 percent shall be added to the amount allocated under section 5306(d) of this title to the State in which the city is located and the city shall be eligible in such succeeding fiscal year to receive a distribution from the State allocation under section 5306(d) of this title as increased by this sentence. Any unit of general local government that was classified as a metropolitan city in any fiscal year, may, upon submission of written notification to the Secretary, relinquish such classification for all purposes under this chapter if it elects to have its population included with the population of a county for purposes of qualifying for assistance (for such following fiscal year) under section 5306 of this title as an urban county under paragraph (6)(D). Any metropolitan city that elects to relinquish its classification under the preceding sentence and whose port authority shipped at least 35,000,000 tons of cargo in 1988, of which iron ore made up at least half, shall not receive, in any fiscal year, a total amount of assistance under section 5306 of this title from the urban county recipient that is less than the city would have received if it had not relinquished the classification under the preceding sentence. Notwithstanding any other provision of this paragraph, with respect to any fiscal year beginning after September 30, 2007 , the cities of Alton and Granite City, Illinois, shall be considered metropolitan cities for purposes of this chapter.