Homelessness emerged as a national issue in the 1870s. Many homeless people lived in emerging urban cities, such as New York City. Into the 20th Century, the Great Depression of the 1930s caused a devastating epidemic of poverty, hunger, and homelessness. There were two million homeless people migrating across the United States. In the 1970s, the de-institutionalization of patients from state psychiatric hospitals was a precipitating factor which seeded the population of people that are homeless.
The number of homeless people grew in the 1980s, as housing and social service cuts increased. After many years of advocacy and numerous revisions, PresidentRonald Reagan signed into law the McKinney–Vento Homeless Assistance Act in 1987—this remains the only piece of federal legislation that allocates funding to the direct service of homeless people. Over the past decades, the availability and quality of data on homelessness has improved considerably. About 1.56 million people, or about 0.5% of the U.S. population, used an emergency shelter or a transitional housing program between October 1, 2008 and September 30, 2009. Homelessness in the United States increased after the Great Recession in the United States.
One out of 50 children or 1.5 million children in United States of America will be homeless each year. In 2013 that number jumped to one out of 30 children, or 2.5 million. There were an estimated 57,849 homeless veterans estimated in the United States during January 2013, or 12 percent of all homeless adults. Just under 8 percent of homeless U.S. veterans are female. Texas, California and Florida have the highest numbers of unaccompanied homeless youth under the age of 18, comprising 58% of the total homeless under 18 youth population. Homelessness affects men more than women. At least 70% to 85% of all homeless are men.
Because of turnover in the population of people that are homeless, the total number of people who experience homelessness for at least a few nights during the course of a year is thought to be considerably higher than point-in-time counts. A 2000 study estimated the number of such people to be between 2.3 million and 3.5 million. According to Amnesty International USA, vacant houses outnumber homeless people by five times.