Capital gains on partial property sale

[glgrivna]

With the recent real estate boom in Arizona, our vacant land has appreciated greatly. We would like to split the less desireable portion of the land, sell it, and use the money toward building a house on the other half. However we do not understand the capital gains involved when splitting a portion of land. Can the entire purchase price of the original lot and other investment costs be applied toward the split off piece that is being sold? If so, this would delay our capital gains until we sell the primary piece of land?