I have been doing a great deal of research into the immigration of Murdock's into Indiana, Illinois, and Iowa in an attempt to locate the parents of my GGG Grandfather William Henry Murdock (b. 1824 in IN, OH, or VT.) He married Susannah Hill in 1848 and resided in Whiteside Co. Ill.
As a result I have been focusing on Murdock's in the 1800 - 1850 period in IN, ILL, and IA. The Wichita KS public library has a HUGE geneology research library with many items not readily available elsewhere. If you are looking for some specific Murdock data in this period in these states let me know and I will see if there is anything in my notes from my own research.