what was the value of the U.s. dollar in several representative years,
such as 1860 1880  1900 2000 ?

Hi! Thanks for the question.

Here are the different values of the US Dollar according to the
Economic History website. Their data only goes till the value compared
to 2004 but you can get a pretty good idea of the value with this
website. Let us measure it using the Consumer Price Index since it is
the most familiar and easy to understand concept because it represents
the value of food, housing, transportation, or other daily expenses.

If you have $1, here are the values as compared to the years you mentioned.

1860 - $22.59
1880 - $18.37
1900 - $22.37
2000 - $1.10

Please refer to this website to get the values: http://eh.net/hmit/compare/

Search strategy used:  
Searched at Eh.net

I hope this link would help you in your research. Before rating this
answer, please ask for a clarification if you have a question or if
you would need further information.
                                                          
                              
Regards,                              
Easterangel-ga                              
Google Answers Researcher

Great speed in answering !

Thanks for the kind words, the 5 stars and for the generous tip! :)