Complex sentence: Cornish was the first to establish an African-American Presbyterian church and Russwurm was a member of the Haytian Emigration Society, to organize free blacks to emigrate to Haiti after its achieving independence in 1804.
Split into simpler sentences: Cornish was the first to establish an African-American Presbyterian church and Russwurm was a member of the Haytian Emigration Society. This group recruited and organized free blacks to emigrate to Haiti after its slaves achieved independence in 1804.