For a short time in the early 1840's Lavinia took her family to Nauvoo, where they continued their association with the Church. But by 1843 they had returned to Tennessee. Their stay in Tennessee was not to last. Lavinia was soon infected with the desire to go west to California.
In a lecture he gave in 1896, one of Lavinia's sons, William Murphy, described their move west.
Yes, that's right, the Donner Party; famous for how the survivors fed themselves in the face of starvation [if you don't know what I'm talking about, go look it up]. The events that led to the deaths of two thirds of the Donner party are beyond the scope of this post. But the party found themselves trapped in the Sierra Nevada mountains in the winter of 1846/47. Lavinia did not make it. She died in a hastily built snowbound cabin the last week of March 1847, too weak and frail to be rescued. Seven of the family survived: five of her children, one son-in-law and one grandchild. Five others did not survive: two of her children, one son-in-law and three grandchildren.
"In 1845 we heard wonderful stories of a wonderful country in the far West, between the Pacific ocean and the Rocky mountains, a country of sulubrious climate, perrenial spring time indeed, of deep and inexhaustible soil, why, they said that wheat grew wild higher than a man's head, and the Mexican Government that exercised some kind of control over it, would grant land to settlers; so my mother, was a widow, with seven children, two sons-in-law and three grand children, suggested that we emigrate to the far off fairy land. She ordered a suitable wagon to be manufactured, a son-in-law did the same, and early in 1846, we started out with two ox teams from West Tennessee, crossed the State of Kentucky, the Ohio river below Paducah, up through Illinois, to Ballville, opposite St. Louis, crossed the Mississippi there, taking a family of three of ours who lived there, completing our number-thirteen. Across the State of Missouri to Independence, then the great entry port of the overland trade of Northern Mexico and Santa Fe; here we learned that the great overland caravan for Oregon and California had departed. We concluded to overtake them, which we did at the Big Blue, in Kansas, where they were water bound. Here we first met the Donners.