New Land: A Novel for Boys and Girls

Teenage twins, Charley and Sayre, follow their widowed father, along with their baby sister, out to Wyoming during the Great Depression, to prove up on some land. They face all sorts of challenges, including dishonest folks and uncooperative nature, but make good in the end.
A bit dated now, but likely seen as fighting the good fight against stereotyping girls back in the day (Sayre works just as hard as her twin brother on the farm and against their rivals). The story itself was fairly engaging, too.