Below is a copy of a postcard mailed in the US back in 1909 -- notice that the cost to mail a postcard that year was a penny. Today, the US postage rate for postcards is 30 cents. Said another way, the price of a US postcard stamp in 1909 was 97% less than today.
Said still another way, the US dollar has lost 97% of its purchasing power during the past century (at least when it comes to mailing postcards). Assuming that inflation remains on that same trajectory in the coming century, the cost of a postcard stamp in the year 2109 will be $9.00, up from $0.30 today.
PS: The reverse side of the above postcard appears below.
PPS: Wallace, Idaho has not changed much over the years -- you can visit their website by following the link below.
Historic Wallace, Idaho