Abstract: Anomalously high nitrogen-to-oxygen abundance ratios [N/O] are observed in globular clusters (GCs), among the field stars of the Milky Way (MW), and even in the gas in a z ≈ 11 galaxy. Using data from the APOGEE Data Release 17 and the Gaia Data Release 3, we present several independent lines of evidence that majority of the MW’s high-[N/O] stars were born in-situ in bound clusters during early, pre-disk evolution of the Galaxy. Specifically, we show that distributions of metallicity [Fe/H], energy, vertical component of the angular momentum, and distance of the high-[N/O] stars with [Fe/H] < −1 match the corresponding distributions of stars of the Aurora population and of the in-situ GCs. We show that the fraction of field high-[N/O] stars decreases by more than an order of magnitude as metallicity increases from [Fe/H] ≈ −1.5 to [Fe/H] > −1.  We also estimate the fraction of such stars in surviving GCs and find that it does not depend on metallicity. We show that these results indicate that up to 50%-70% of the in-situ star formation at [Fe/H] ≈ −1.5 occurred in bound clusters, while at higher metallicities this fraction dropped by more than a factor of ten. This implies that star formation in bound clusters was a significant mode of star formation in the early Galaxy. In contrast, similar estimates for the accreted stars indicate a much smaller fraction of clustered star formation times in accreted dwarfs at similar metallicities.