Letters from a liberated frontier woman; Letters of a Woman Homesteader, by Elinor Pruitt Stewart. Boston: Houghton Mifflin Company. 282 pp. $5.95.

First published in 1914, these lively letters from a former washerwoman who moved from Colorado to Wyoming in the early 1900s are packed with the action of pioneer life.

Elinor Pruitt Stewart writes of day-to-day work on her homestead: growing vegetables and fruits, milking 10 cows, selling enough butter to pay for a year's supply of flour and gasoline, raising chickens and turkeys - and three children. When she's not working, she's camping out along the Wind River Basin and glorying in the mountain vistas that surround her.

Best of all, her adventures are peopled with the kinds of characters most novelists only dream of: Zebulon Pike Parker, a transplanted Southerner who fiddles away his memories into the night; and Gavotte, a French trapper who cares for critters by winter and hunts fossils in the Badlands by summer.