Hello Ingrid,
For some reason, I was never notified that you posted a query requesting information. I am sorry that it has taken me so long to get back to you. I looked in the book and I did not find any Briggs mentioned. I also checked the Washington Digital Archives that listed many Briggs, but I did not find a child born in 1919 as Margrett was. I noticed that there is a son in the household (possibly Oskar) who is indexed as being 4 months old born in Colorado and Margrett is indexed to be 2 months born in Washington. That doesn't seem to make sense.

You might search the Washington Digital Archives to see if you might find something:

http://www.digitalarchives.wa.gov/

I am sorry that I wasn't able to help you,
Eellitta