Trailers provide housing at a lower cost than conventional foundation-built houses. In past decades trailers had few amenities which led to the popular cultural conception that those who live in trailer parks are usually only those who are too poor to afford anything else.
Modern manufactured mobile homes, which are identical to homes built in pre-fabricated housing developments, are rapidly replacing the single- and double-wide trailer that most associate with traditional trailer parks.
Because trailer parks require a large amount of space, they are found mostly in rural areas or on otherwise undesirable land in the suburbs. These factors combine to make trailer trash equivalent to "poor, rural, and white".
See also: white trash.