Aug. 26 -- Gov. Blanco declares a "state of emergency" under Louisiana law. This declaration does not identify any particular localities. It is general in nature.
http://www.gov.state.la.us/2005%20%20proclamations/48pro2005-Emergency-HurricaneKatrina.pdfAug.27 -- Gov. Blanco sends letter to POTUS requesting that he "declare an emergency", beginning Aug 26, 2005, under federal law. The letter does not name specific parishes; rather it describes the impacted area as follows: "The affected areas are all the southeastern parishes including the New Orleans Metropolitan area and the mid state Interstate I-49 corridor and northern parishes along the I-20 corridor that are accepting the thousands of citizens evacuating from the areas expecting to be flooded as a result of Hurricane Katrina."
http://www.gov.state.la.us/Press_Release_detail.asp?id=976Aug. 27 -- The White House declares an emergency (effective Aug 26) in Louisiana. The declaration contains a list of around 40 named parishes. That list does not include Orleans, Plaquemines, or other parishes along the coast.
http://www.whitehouse.gov/news/releases/2005/08/20050827-1.htmlAug. 28 -- Gov. Blanco sends letter to POTUS requesting declaration of major disaster in Louisiana. Letter indicates major damage is expected in specified parishes, including Orleans, Plaquemines, etc. Another group of parishes are identified as anticipating sigificant damage. A third group of parishes are identified as being affected by the evacuation of persons from other parts of the state. The third list of parishes is similar, but not precisely identical, to the list of parishes in the White House declaration from the day before.
http://www.gov.state.la.us/Disaster%20Relief%20Request.pdf
August 29 -- The White House declares a major disaster for Louisiana. The declaration identifies three groups of parishes, precisely tracking the listsing of parishes in Gov. Blanco's request from the day before. This is the first federal document to mention Orleans parish or New Orleans specifically.
http://www.whitehouse.gov/news/releases/2005/08/20050829-2.htmlonenote