Secretary of State   Department of State (1789):

Highest ranking Cabinet officer
Negotiates with foreign countries

Protects foreign interests in other countries,

Attends ceremonies for pres and VP, heads U.S. delegation at funerals,

Secretary of the Treasury  Department of the Treasury (1789):
Supervises the collection of taxes and the printing of money.

Includes IRS, U.S. mint, Customs Service, Secret Service, BATF

Secretary of Defense  Department of Defense (1947):
Sec advises pres on matters of weapons systems, military preparedness, troop strength

Oversees the armed forces: more than 3 million employees- army, navy, marine corps, air force

Attorney General  Department of Justice (1870):
Enforces the U.S. federal laws.

Advises pres on legal issues

Represents government in court

Oversees FBI, Drug Enforcement Agency, Immigration and Naturalization Service, Bureau of Prisons

Secretary of the Interior  Department of the Interior (1849):
Protects natural resources and wildlife.

Administers more than  500 million acres of fed land, incl. National parks

Oversees use & conservation of natural resources:

minerals, water, fish, wildlife, forests

Secretary of Agriculture  Department of Agriculture (1862):
Ensures a healthy food supply and provides support for farmers.

Oversees farm-related activities

Monitors quality of nation’s food supply

Administers food & nutrition assistance services (food stamp program)

Secretary of Commerce   Department of Commerce (1903):
Reports to pres on matters of trade, business, industry

Promotes business and job opportunities for all Americans

Responsible for all copyrights, patents, and trademarks

Secretary of Labor  Department of Labor (1913):
Oversees the interests of U.S. workers.

Advises pres on labor-related matters such as labor statistics, occupational health and safety concerns

Secretary of Health & Human Services
Department of Health and Human Services (1953):
Looks after people's health and provides services:

medical research, disease control, substance abuse prevention

financial assistance for low income families. 

Agencies: FDA,  Aid to Families with Dependent Children, Medicare and Medicaid

Secretary of Housing & Development
Department of Housing and Urban Development (1965):
Improves and develops communities, e.g. renovates city slums

Assists citizens with housing needs, such as Gov National Mortgage Assoc, and Fair Housing programs

Secretary of Transportation  Department of Transportation (1966):
Oversees the nation's transportation system including highways, railroads, ports, and air travel.   Responsible for safety of public travel

Secretary of Energy  Department of Energy (1977):
Researches & develops energy systems that are friendly to the environment, but are not too expensive.  

Oversees nation’s fuel needs, oil reserves, nuclear energy

Secretary of Education   Department of Education (1979):
Establishes guidelines & provides leadership for American education.

Helps local communities meet students’ needs

Provides federal student aid (loans)

Protects civil rights, equal opportunity

Secretary of Veterans Affairs  Department of Veterans Affairs (1988):
Operates programs for veterans and their families.

Oversees programs for veterans including housing, medical care, etc.

Secretary of Homeland Security 
Department of Homeland Security (2003): 
newest department; created after 9-11
Works to prevent terrorist attacks within the United States, reduce America's vulnerability to terrorism, and minimize the damage from potential attacks and natural disasters.