Bodenhorn says “by 1820...banks became better known, more reputable, more established, and therefore more trusted,” presumably convincing more people (whether as shareholders or depositors) to put their money in banks. This is capital deepening, a supply-side argument: growth happened when banks began to accumulate enough money to lend to industrialists or invest. There’s so little written about banking since Bray Hammond, this is a must-read.