Little is known about how individual virus lineages replicating during acute Human Immunodeficiency Virus or Simian Immunodeficiency Virus (HIV/SIV) infection persist into chronic infection. In this study, we use molecularly barcoded SIV (SIVmac239M) to track distinct viral lineages for 12 weeks after intravenous and intrarectal challenge in macaques. Two Mafa-A1*063+ cynomolgus macaques (Macaca fascicularis) were challenged intravenously (IV), and two Mamu-A1*001+ rhesus macaques (Macaca mulatta) were challenged intrarectally (IR) with 200,000 Infectious Units (IU) of SIVmac239M. We deep sequenced the molecular barcode from all animals over 12 weeks to characterize the diversity and persistence of virus lineages, as well as the sequences of T cell epitopes during acute SIV infection. During the first three weeks post-infection, we found ~175-950 times more unique virus lineages circulating in the animals challenged intravenously than those challenged intrarectally, suggesting that challenge route is the primary driver restricting the transmission of individual viral lineages. Additionally, the emergence of escape variants can occur on multiple virus templates simultaneously, but elimination of some templates is likely a consequence of additional host factors. These data imply that virus lineages present during acute infection can be eliminated from the virus population even after initial T cell selection.