Exhibit 4.1 AMENDMENT NO. 1 TO RIGHTS AGREEMENT Amendment No. 1, dated as of September 24, 2004 to the Rights Agreement dated as of March 30, 1999 (the "Agreement"), between KeySpan Corporation (f/k/a MarketSpan Corporation), a New York corporation...Rights Agreement • September 24th, 2004 • Keyspan Corp • Natural gas distribution • New York
