Block from U+1100 to U+11FF. This block was introduced in Unicode version 1.1 (1993). It contains 256 codepoints.
The Wikipedia provides the following information on block Hangul Jamo:
Hangul Jamo is a Unicode block containing positional (Choseong, Jungseong, and Jongseong) forms of the Hangul consonant and vowel clusters. They can be used to dynamically compose syllables that are not available as precomposed Hangul syllables in Unicode, specifically archaic syllables containing sounds that have since merged phonetically with other sounds in modern pronunciation.