Website Showing no Padlock due to Mixed Content - HELP

Good evening community --
I've been attempting to fix this for awhile now, but I cannot find the Google Maps API insert that is causing my website to not display the "padlock" that shows it's secured, https.

In my findings, I have noticed the following address as not being secured so it's showing "mixed content".

http://csi.gstatic.com/csi?v=2&s=mapsapi3&v3v=26.14&action=apiboot2&e=10_1_0,10_2_0&rt=main.8

With that being said, I cannot find what is causing this to be displayed.

Anyone that is smarter than me know how to find what is causing this and get it fixed?

https://www.cityofhanahan.com is our website.

Thank you,
David