Would seat 19A be an aisle seat or a window seat on American Airlines 738?

19A is a window seat. The Seating chart moves as follows:

(Bulkhead ABC-Aisle-DEF Bulkhead) in Economy

First Class is:

(Bulkhead AB-Aisle-EF Bulkhead)

Row 19 is approximately a row or two past the wing 'flaps' of a 737.