Order of precedence - America's seating chart
- President of the United States
- Vice-president of the United States
- Governor (in own state)
- Mayor (in own city)
- Speaker of the House of Representatives
- Chief Justice of the United States
- Former Presidents of the United States
- American Ambassadors (at Post)
- Secretary of State
- Secretary General of the United Nations
- Ambassadors Extraordinary and Plenipotentiary of Foreign Powers accredited to the United States (in order of the presentation of their credentials)
- Widows of former Presidents of the United States
- Ministers of Foreign Powers accredited to the United States
- Associate Justices of the Supreme Court
- Retired Chief Justices
- Retired Associate Justices of the Supreme Court
- Members of the Cabinet
- President Pro Tempore of the Senate
- Senators (according to length of continuous service)
- Governors (when outside own state)
- Former Vice Presidents
- Members of House of Representatives (according to length of continuous service
Retired military officials seem to retain quite a high social ranking. Retired 4-star Generals and Admirals rank directly below active duty officers of the same rank and above active duty 3-stars.
State Governors are ranked by the order of their state's admission to the union, but Senators and members of Congress are ranked by personal senority.
Wikipedia has a nice (but incomplete) order of precedence page that shows which retired officials and widows are still around, plus how long each member of Congress has held office here.
I couldn't find where ordinary American citizens rank socially...