Historical clue formulations

• South America's Río de la ___ — 2021-12-31
• Montana motto word — 2018-02-02
• Señorita's silver — 2013-04-18
• Silver, in the Sierra Madres — 2012-09-26
• Oro y ___ (Montana's motto) — 2010-12-13
• Oro y ___ (motto of Montana) — 2008-11-12
• La ___, capital of Buenos Aires province — 2008-06-21
• South American silver — 2006-05-12
• Oro y ___ (Montana's motto) — 2004-08-10
• La ___, port near Buenos Aires — 2004-06-11
• Metal in Montana's motto — 2003-03-28
• City once named Eva Peron, with "La" — 1996-10-13
• Rio de la _____ — 1995-04-24