The average of the New York Fed's Empire State and the Philadelphia Fed's manufacturing general activity indexes. Both are published in the same month they survey, weeks before the national ISM, and are free to reuse.
Threshold source: Diffusion index convention: below zero more firms report falling than rising activity. How thresholds are chosen
Two districts, manufacturing only, and noisy month to month. A single negative print means little; two in a row is the threshold for that reason.