Insmed (INSM) had the highest return in January 2019 by a large-cap US stock or large-cap US stock, returning 86.6%.

ASSET	MONTH	% RETURN
Insmed (INSM)	January 2019	86.57%
Roku (ROKU)	January 2019	50.74%
Centrais Elétricas Brasileiras SA - Eletrobrás (AXIA)	January 2019	48.76%
Centrais Electricas Brasileiras (EBR)	January 2019	48.76%
EXACT Sciences (EXAS)	January 2019	45.57%
Companhia de Saneamento Basico do Estado de Sao Paulo SABESP ADR (SBS)	January 2019	43.81%
Centrais Elétricas Brasileiras SA - Eletrobrás (EBR.B)	January 2019	43.04%
Carpenter Technology (CRS)	January 2019	36.43%
GE Aerospace (GE)	January 2019	36.19%
Advanced Micro Devices (AMD)	January 2019	35.54%
Okta (OKTA)	January 2019	34.91%
PDD (PDD)	January 2019	32.77%
Block (XYZ)	January 2019	31.89%
Bilibili (BILI)	January 2019	31.5%
Flex (FLEX)	January 2019	31.42%
Aptiv (APTV)	January 2019	31.12%
Netflix (NFLX)	January 2019	30.94%
Texas Pacific Land Trust (TPL)	January 2019	30.65%
Tenet Healthcare (THC)	January 2019	30.35%
Teva Pharma Industries Ltd ADR (TEVA)	January 2019	30.25%
Somnigroup International (SGI)	January 2019	30.11%
Synchrony Financial (SYF)	January 2019	29.76%
Facebook (META)	January 2019	29.23%
HubSpot (HUBS)	January 2019	29.15%
MKS Instruments (MKSI)	January 2019	29.06%

Large-cap stocks are treated as having a market cap of $10B+.