West Africa Profile

My travels covered 3 countries: Mali, Senegal, and Gambia. This is the poorest and least developed region in the world. Of 16 countries in West Africa, not a single one is on the OECD list of developed countries. In fact, all 16 rank "low" (bottom 40) on the human development index. 8 are in the 20 least developed in the world, and 5 are in the 10 least developed (including Mali).
A few pertinent facts to provide perspective:

Religion: 90% Muslim
Polygamy: Prevalent

Languages: Dozens of tribal languages are the first tongue for almost everyone. Majority in Mali-Bambara; in Senegal-Wolof; in Gambia-Mandinka. The official language taught in schools is French (Mali and Senegal) or English (Gambia).

Mali
Human Development Index (How much is developed?): 30.9%
Population: 13.1 million
Life expectancy: 49 yrs
Under five mortality rate (% of kids who die before their 5th birthday): 19.1%
Lifetime risk of maternal death (how many women will die related to childbirth): 1 in 22
Rate of Female Genital Cutting: 85%
Number of physicians/population: 8/100,000
Total Literacy (% of population who can read): 26%
Female literacy (% of women who can read): 12%
Rate of Child Marriage (% of people married before the age of 18): 71%
Percent of population living on less than $2/day: 77.1%
GDP per capita: $392/yr
Percent of people with phone access: 27%
Percent of people with internet access: 2%

Senegal
Human Development Index: 41.1%
Population: 12.5 million
Life expectancy: 56
Under five mortality rate: 9.3%
Lifetime risk of maternal death: 1 in 46
Rate of Female Genital Cutting: 28%
Number of physicians: 6.9/100,000
Total Literacy: 42%
Female literacy: 29.2%
Rate of Child Marriage: 39%
Percent of population living on less than $2/day: 60.4%
GDP per capita: $707/yr
Percent with phone access: 44%
Percent with internet access: 8%

Gambia
Human Development Index: 39%
Population: 1.7 million
Life expectancy: 56
Under five mortality rate: 10.3%
Lifetime risk of maternal death: 1 in 49
Rate of Female Genital Cutting: 78%
Number of physicians: 11/100,000
Total Literacy: 45%
Female literacy: 27%
Rate of Child Marriage: 36%
Percent of population living on less than $2/day: 82.9%
GDP per capita: $304/day
Percent with phone access: 70%
Percent with internet access: 7%

United States
Human Development Index: 90%
Population: 314.6 million
Life expectancy: 79
Under five mortality rate: 0.8%
Lifetime risk of maternal death: 1 in 2100
Number of physicians: 230/100,000
Literacy: 99%
Percent of population living on less than $2/day: (I would assume <5%)
GDP per capita: $47,123
Percent with phone access: 87%
Percent with internet access: 74%

*Sources:
Lonely Planet
Wikipedia
UNICEF
World Development Indicators