[6] Besides North America, dialects of ASL and ASL-based creoles are used in many countries around the world, including much of West Africa and parts of Southeast Asia.

ASL originated in the early 19th century in the American School for the Deaf (ASD) in Hartford, Connecticut, from a situation of language contact.

Reliable estimates for American ASL users range from 250,000 to 500,000 persons, including a number of children of deaf adults (CODA) and other hearing individuals.

[8]: 14  That suggests nascent ASL was highly affected by the other signing systems brought by the ASD students although the school's original director, Laurent Clerc, taught in LSF.

[7]: 7 [8]: 14  In fact, Clerc reported that he often learned the students' signs rather than conveying LSF:[8]: 14 I see, however, and I say it with regret, that any efforts that we have made or may still be making, to do better than, we have inadvertently fallen somewhat back of Abbé de l'Épée.

[9]: 501  There are modality-specific reasons that signed languages tend towards agglutination, such as the ability to simultaneously convey information via the face, head, torso, and other body parts.

[9]: 502  Additionally, Clerc and Thomas Hopkins Gallaudet may have used an artificially constructed form of manually coded language in instruction rather than true LSF.

[10]: 69  However, that does not seem justified historically for ASL and Auslan, and it is likely that the resemblance is caused by the higher degree of iconicity in sign languages in general as well as contact with English.

[7]: 5  As early as 1541 at first contact by Francisco Vásquez de Coronado, there were reports that the Indigenous peoples of the Great Plains widely spoke a sign language to communicate across vast national and linguistic lines.

[14]: 80 In the 19th century, a "triangle" of village sign languages developed in New England: one in Martha's Vineyard, Massachusetts; one in Henniker, New Hampshire, and one in Sandy River Valley, Maine.

[7]: 5–6  MVSL was used even by hearing residents whenever a deaf person was present,[7]: 5–6  and also in some situations where spoken language would be ineffective or inappropriate, such as during church sermons or between boats at sea.

[7]: 4  Originally known as The American Asylum, At Hartford, For The Education And Instruction Of The Deaf And Dumb, the school was founded by the Yale graduate and divinity student Thomas Hopkins Gallaudet.

[8]: 11  Laurent Clerc, the first teacher at ASD, taught using French Sign Language (LSF), which itself had developed in the Parisian school for the deaf established in 1755.

However, the efforts of Deaf advocates and educators, more lenient enforcement of the Congress's mandate, and the use of ASL in religious education and proselytism ensured greater use and documentation compared to European sign languages, albeit more influenced by fingerspelled loanwords and borrowed idioms from English as students were societally pressured to achieve fluency in spoken language.

[22] Recognition of the legitimacy of ASL was achieved by William Stokoe, a linguist who arrived at Gallaudet University in 1955 when that was still the dominant assumption.

[25]: 1 [d] The ultimate source for current estimates of the number of ASL users in the United States is a report for the National Census of the Deaf Population (NCDP) by Schein and Delk (1974).

[25]: 1, 21  A 100,000-person lower bound has been cited for ASL users; the source of that figure is unclear, but it may be an estimate of prelingual deafness, which is correlated with but not equivalent to signing.

[25]: 15, 22  Those figures misquote Schein and Delk (1974), who actually concluded that ASL speakers constituted the third-largest population "requiring an interpreter in court".

[26]: 410  Such signing systems are found in Benin, Burkina Faso, Ivory Coast, Ghana, Liberia, Mauritania, Mali, Nigeria, and Togo.

[26]: 411 In addition to the aforementioned West African countries, ASL is reported to be used as a first language in Barbados, Bolivia, Cambodia[27] (alongside Cambodian Sign Language), the Central African Republic, Chad, China (Hong Kong), the Democratic Republic of the Congo, Gabon, Jamaica, Kenya, Madagascar, the Philippines, Singapore, and Zimbabwe.

The most notable production difference of hearing people learning American Sign Language is their rhythm and arm posture.

That limited access to signers from other regions, combined with the residential quality of Deaf Schools promoted specific use of certain sign variants.

[41] Scholars such as Beth S. Benedict advocate not only for bilingualism (using ASL and English training) but also for early childhood intervention for children who are deaf.

It is alphabetic, with a letter or diacritic for every phonemic (distinctive) hand shape, orientation, motion, and position, though it lacks any representation of facial expression, and is better suited for individual words than for extended passages of text.

[45]: 163  That assertion has been disputed, and the process for each country to look at the ISWA and create a phonemic/morphemic assignment of features of each sign language was proposed by researchers Msc.

[7]: 1 ASL has a rich system of verbal inflection, which involves both grammatical aspect: how the action of verbs flows in time—and agreement marking.

Inflection, on the other hand, involves modifying a word's form to indicate grammatical features such as tense, number, gender, person, case, and degree of comparison.

In American Sign Language (ASL), inflection is conveyed through facial expressions, body movements, and other non-manual markers.

By studying morphemes and how they can be combined or modified, linguists gain insight into the underlying structure of language and the creative ways in which it can be used to express meaning.

[63] In the era of the influential linguist Ferdinand de Saussure, it was assumed that the mapping between form and meaning in language must be completely arbitrary.