Beyond that, I don't have a lot to offer. Until yesterday, all we had was Catherine Sieferts name.I'm not sure without the family book in front of me. I THINK Catherine was my ggg grandmother. I may be one "great" over or under, not sure.
First order of business. How does your family line pronounce "Siefert"?
Now my mom has heard older family speak aloud the name pronounced as Syyfert. In other words, they rather strangely pronounce ie as a long i or y. This is not a usual pronunciation of ie in Either English or German as far as I know. Has anyone in your family passed down their pronunciation of the name?
It's important to have a best idea as to the passed down pronunciation. The spelling is less important. I am new at this but find that many Germans changed the spelling of their name but not so much the phonetics. Well before World War I anyway.
This may explain why neither you or I am finding Lawrence "Siefert" on an immigrant list. If they kept the phonetics but changed the spelling we are looking for the wrong name. I'll work my end on different phonetics of S(long I)fert and see what that turns up.
I am in Wichita Ks. But I have extensive family in the Sarcoxie area. So that might be a little help on the ground. And my Mom will be joining us on the net search just as soon as her ISP is hooked up.