Thanks so much for clearing up that mystery. I had suspected that Mary Unknown was Mary Fowler since in the 1880 U.S. census William Brazee was living with the Jess Fowler family and was referred to as "grandson". Here is what I now know:
Arthur M. Lowe did NOT marry the daughter of Andrew A Brazee & Marium Webb. Their daughter Mary Brazee married Thomas J Fradenburg 30 Oct 1889 in Clark County, WA.
Arthur M. Lowe married Mary C Brazee, the daughter of James Vincent Brazee & Mary Fowler. Mary C Brazee was fostered at the home of Moses Webb & Mary E Davis from before 1870 until 1886. Mary C Brazee had an illegitimate child (Mary May b 1881/1882) while living with Moses Webb & Mary E Davis. Arthur M. Lowe & Mary C Brazee married 18 Jul 1886 at the home of Moses Webb & Mary E Davis in Cowlitz County, WA. The wedding was performed by Nathan Davis, the father of Mary E Davis who lived next door. They remained married until Mary C Brazee's death 2 Aug 1915.
I am unable to locate the Fowlers in 1850. I don't know if they were still in Missouri, in transit on the Oregon Trail or in Washington by this time.
The wife of James V Brazee is Mary Fowler, the daughter of Jess Fowler & Margaret. By 1870 James & Mary had divorced or more likely is that Mary had died. By 1870 the family was split up. The children Richard, Cynthia, William D, Albert L, and Mary C Brazee were distributed among other families and their father James V Brazee hired out as farm labor. James died 18 Nov 1908.
Moses Webb is related to James V Brazee. They are cousins. James V Brazee's mother was Hannah Webb. The father of Moses Webb was Benjamin Webb. Benjamin and Hannah were brother and sister. The two families came to Washington together on the Oregon Trail in 1853. They passed through the Umatilla Agency in eastern Oregon and were recorded in a census there 14 Sep 1853.
I have also traced these Webb's back to John Webb Jr. & Mary Boone, who was the daughter of George Boone III. George III was Daniel Boone's grandfather.