Spatially resolved emission current density maps are presented as a function of extraction voltage for two near-conical porous borosilicate glass electrospray emitters using a 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imid ionic liquid. The current measurements are complimented with time-of-flight measurements to characterize the charge-to-mass ratio of the beams. The spatial current probe measurements resolve individual beamlets associated with separate emission sites, allowing the observation of the growth of the number of emission sites as the extraction voltage is increased. The emitters are found to operate near the pure ionic regime, and no evidence of the transition to unstable emission is observed up to above onset. An empirical model is developed for the onset of emission sites that accounts for the changes in site hydraulic resistance with the number of emission sites. The model satisfactorily reproduces the experimental voltage–current curves and average beam charge-to-mass ratios after the adjustment of several empirical parameters.