The 'older' ginghams were 100% cotton.
Now one does need to check the end of the bolt to see what the fiber content is.
One can do a burn test to see what your older pieces are made of. One only needs a piece about 1/4 x 1 inch long -
http://quilting.about.com/od/fabrice.../burn_test.htm
That quilt that was pictured is lovely. Very fresh and bright looking.