We analyze the dependence of entanglement in the 1D Heisenberg model on temperature and external field. We find that the entanglement between two spins in an antiferromagnetic solid can be increased by increasing the temperature or the external field. Increasing the field to a certain value can also create entanglement between otherwise disentangled spins. However, on exceeding a critical value of the field, the entanglement vanishes at zero temperature and decays off at a finite temperature. In the ferromagnetic solid, on the other hand, entanglement is always absent. We also compare the entanglement in these systems to the total correlations.