Under the 10th amendment of the constitution, the constitution reserves to the states all powers not specifically granted to the federal government. an example of a power reserved to the states is:

The Tenth Amendment declares, "The powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people." In other words, states have all powers not granted to the federal government by the Constitution.

These powers have taken many different forms. States must take responsibility for areas such as:

ownership of property
education of inhabitants
implementation of welfare and other benefits programs
distribution of aid
protecting people from local threats
maintaining a justice system
setting up local governments such as counties and municipalities
maintaining state highways
setting up the means of administrating local roads
regulation of industry
raising funds to support their activities

:D hope i helped

From mexican american war , us gained new mexico.