I am researching Caterpillar inc. and I need some direction. I need to find out what investment banks Caterpillar uses to issue their stock?

I find the fastest way to find info like this is directly from the company:
Caterpillar: Home (http://www.cat.com/cda/layout?m=8703&x=7)

Generally there will be a stockholder/investor section right from the home page, which will contain not only their annual reports, but other information of interest to investors.