Unfortunately the strike is fairly weak, but it's not a cancel I've ever seen before. Inquiry to the usual revenue experts has come up empty, so time to engage in "crowdsleuthing".
It appears that there were a number of pharmacies on Madison St. in Chicago in the mid-to-late 19th century, but I'm not coming up with anything associated with "Williams" on Madison St. There's an 1877 directory of Illinois Homeopathic Pharmacies that comes up with nothing, and an 1870 Chicago city directory doesn't come up with anything with 40 in the address either.
My attempt at the cancel text:
240 W. Madison St.
Can anyone help with the attribution or perhaps a better strike?