My favorite wildflower identification site has this to say about it:
This native of the Mediterranean region is considered a weed.
Chicory has been used for salad greens and the root as a coffee substitute.
The flowers are usually blue, but can occasionally be white.
The flower heads open in the early morning and close around noon on bright days.
Native Americans boiled the roots to make a wash for fever sores and steeped the roots to create a nerve tonic.
Chicory has a deep taproot.
Will give a bitter taste to milk when consumed by dairy cattle.
I find the factoid of it opening early in the morning and closing around noon to be very interesting!